Other smart (serial bus) servos · Servo Guide

Comparison table

Unit	Price	Torque	Speed	Weight	Interface	Status
Feetech STS3215 (ST-3215)	$13.89 – $23.99	1.91 N·m at 7.4 V (C001)	about 52 rpm at 7.4 V (C001)	55 g	TTL half-duplex asynchronous…	Available
Waveshare ST3215 / ST3215-HS / ST3235	$16.99 – $21.99	1.91–2.94 N·m by version	45 rpm at 12 V	about 55–70 g	TTL serial bus	Available
Feetech SCS0009	$9.00	0.23 N·m	0.10 s/60° at 6 V	13.2 g	TTL half-duplex serial bus	Available
Feetech SM series (SM45BL, SM85CL)	$141	4.41–8.34 N·m at 24 V	37–70 rpm at 24 V	100–215 g	RS-485 half-duplex serial bus	Available
Hiwonder LX-16A	$16.99	1.67 N·m	0.19 s/60° at 7.4 V	53–54 g	Hiwonder's own UART serial bus…	Available
Hiwonder LX-224HV (and LX-224)	$19.99	1.96 N·m at 11.1 V (HV)	0.18 s/60° at 11.1 V (HV)	62 g	Hiwonder UART serial bus at…	Available
Hiwonder HX-35H (and HX-35HM)	$18.99	3.43 N·m at 11.1 V	0.18 s/60° at 11.1 V	52–71 g	Hiwonder UART serial bus at…	Available
Lynxmotion Smart Servo (LSS) ST1 / HS1 / HT1	about $79 – $121	0.78–2.84 N·m at 12 V	60–100 rpm at 12 V	57–79 g	TTL full-duplex serial	Available
Kondo KRS-2552R3HV / KRS-2572R2HV ICS	about $53	1.37–2.45 N·m at 11.1 V	0.13–0.14 s/60° at 11.1 V	KRS-2552R3HV 41.5 g.…	Kondo ICS 3.6	Available
Kondo KRS-3304R2 ICS	about $61	1.36 N·m	0.11 s/60° at 7.4 V	33.7 g	Kondo ICS 3.6	Available
HerkuleX DRS-0101 (and DRS-0201)	$61.00	1.18 N·m at 7.4 V	0.166 s/60° at 7.4 V	45 g	Full-duplex asynchronous serial	Available

Feetech STS3215 (ST-3215)

Feetech (Shenzhen FEETECH RC Model, China) · 2020 · Available · $13.89 – $23.99

$13.89 per servo on Feetech's Alibaba listings as quoted in the SO-ARM100/101 bill of materials. Seeed Studio sells the 7.4 V C001 at $21.99 ($20.99 at 10+) and the 12 V C047 at $23.99 ($22.99 at 10+). RobotShop also lists the 12 V version at about $32 including US tariffs (unconfirmed). October 2026 check.

Feetech released the magnetic-encoder STS series on April 6, 2020, replacing the potentiometer in its older SCS bus servos with a 12-bit magnetic sensor. The STS3215 became the default actuator of Hugging Face's LeRobot ecosystem when the SO-100 arm launched in late 2024, which made it probably the most widely used smart servo in hobby robot learning. The same 45 × 24.7 × 35 mm body comes in several gear ratios, so SO-101 leader arms mix 1:345 (C001), 1:191 (C044) and 1:147 (C046) units for easy hand-guiding, while followers use six C001s or the stronger 12 V version.

Torque: 7.4 V C001: 1.91 N·m (19.5 kg·cm) stall, which Feetech's C001 page labels at 6 V and Feetech's 2020 launch note and Waveshare label at 7.4 V. TheRobotStudio quotes 1.62 N·m (16.5 kg·cm) at 6 V. Rated 0.64 N·m (6.5 kg·cm) per Feetech or 0.49 N·m (5 kg·cm) per Seeed. 12 V C018/C047: 2.94 N·m (30 kg·cm) stall, 0.98 N·m (10 kg·cm) rated at 12 V
Speed: 7.4 V C001: 0.238 s/60° (about 42 rpm) no load at 6 V, 52 rpm at 7.4 V. 12 V C018: 0.222 s/60° (about 45 rpm) no load at 12 V
Weight: 55 g
Size: 45.2 × 24.7 × 35 mm
Voltage: 7.4 V version 6–7.4 V. 12 V version 4–14 V
Current: 7.4 V C001: 150 mA no load, 2.0 A stall at 6 V. 12 V C018: 180 mA no load, 2.7 A stall at 12 V
Gearing: Metal gears (copper on C001, steel on C018). C001 and C047 1:345, C044 1:191, C046 1:147
Motor: Feetech lists a coreless motor for the 7.4 V C001 (Seeed's listing says iron-core) and an iron-core motor for the 12 V C018/C047
Feedback: 12-bit magnetic encoder (4096 steps/rev). Reports position, speed, load, input voltage, current and temperature
Interface: TTL half-duplex asynchronous serial bus, 38,400 bps – 1 Mbps, IDs 0–253, Feetech SCS/STS protocol, dual 3-pin connectors for daisy-chaining
Range: 360° position mode (0–4095), continuous-rotation motor mode, no mechanical stop
Other: Dual-shaft case (output plus idler shaft) and 25T output spline. Plastic case (PA+GF on the C018 page, though Feetech's C001 page says aluminum alloy). 12-bit encoder means about 0.088° per step

Good for

Cheap closed-loop joints for imitation-learning arms, small RL bipeds and hobby legged robots, where real position, load and temperature readback matter more than precision.

Not good for

Precise or stiff manipulation, since backlash and plastic cases limit accuracy. Torque control is coarse, and continuous high loads overheat the 7.4 V version.

Robots in the guide that use it

SO-101~$230 DIY parts (pair),…

SO-100~$232 DIY parts (pair)

LeKiwi~$450 – $870 complete

XLeRobot 0.4~$800 – $900 all-in

Open Duck Mini v2~$400 DIY · $600 kit ·…

Bimo$500

Z-BotNot for sale · DIY BOM…

Also the servo behind many LeRobot-derived community builds. The Hiwonder NexArm and Waveshare RoArm-M3 use their own or rebranded servos instead.

Sources Feetech ST-3215-C001 spec page ↗ · Feetech ST-3215-C018 (12 V) spec page ↗ · Feetech 2020 STS3215 launch note ↗ · SO-ARM100/101 bill of materials (TheRobotStudio) ↗ · LeRobot SO-101 docs (gear ratios per joint) ↗ · Seeed Studio STS3215 7.4 V C001 ↗ · Seeed Studio STS3215 12 V C047 ↗ · Seeed Feetech servo wiki (variant list) ↗
Buying Seeed Studio stocks the C001 in US and China warehouses and the C047 in US, China and Germany warehouses. Amazon US carries several sellers' packs. Alibaba and AliExpress ship from China, typically 1–3 weeks (unconfirmed).

Waveshare ST3215 / ST3215-HS / ST3235

Waveshare (China), servos appear to be made by Feetech (unconfirmed) · Available · $16.99 – $21.99 (ST3215, ST3215-HS), $49.99 (ST3235)

Waveshare official store, October 2026 check. ST3215 $16.99–$21.99 depending on version, ST3215-HS $21.99, all-metal ST3235 $49.99 ($48.29 at 4+).

Waveshare sells this servo under its own ST3215 name with the same body size, encoder, protocol family and 7.4 V figures as Feetech's STS3215, and its wiki describes it as working with the same SCServo-style commands. It is listed separately here because Waveshare publishes no ST3215 gear ratio and adds its own variants, the fast 106 rpm ST3215-HS and the all-metal ST3235. The RoArm-M3-S uses ST3215 and ST3215-HS servos in plastic cases, while the RoArm-M3-Pro puts five metal-cased ST3235s on every joint except the second wrist joint and the gripper.

Torque: ST3215 12 V: 2.94 N·m (30 kg·cm) at 12 V. ST3215 7.4 V: 1.91 N·m (19.5 kg·cm) at 7.4 V. ST3215-HS: 1.96 N·m (20 kg·cm) at 12 V. ST3235: 2.94 N·m (30 kg·cm) at 12 V
Speed: ST3215 12 V and ST3235: 0.222 s/60° (45 rpm) no load at 12 V. ST3215 7.4 V: 0.192 s/60° (52 rpm) no load at 7.4 V. ST3215-HS: 0.094 s/60° (106 rpm) at 12 V
Weight: ST3215-HS 68 g, ST3235 70.5 g (ST3215 weight not published)
Size: 45.22 × 35 × 24.72 mm (ST3215 and ST3235)
Voltage: 12 V versions 6–12.6 V. 7.4 V version 4–7.4 V
Current: ST3215 12 V: 200 mA no load, 2.7 A locked rotor. 7.4 V: 150 mA no load, 2.5 A locked rotor. ST3215-HS: 240 mA no load, 2.4 A locked rotor. ST3235: 190 mA no load, 2.7 A locked rotor
Gearing: Metal gears. ST3235 1:345 steel gears. ST3215 ratios not published
Motor: ST3235 uses a carbon-brush motor in a CNC aluminum alloy case
Feedback: 12-bit 360° magnetic encoder (4096 steps). Reports position, load, speed and input voltage, and the ST3235 also current and temperature
Interface: TTL serial bus, 1 Mbps default, IDs 0–253, 3-pin 5264/2.54 mm connectors
Range: 360° servo mode (0–4095), continuous motor mode, no mechanical limit
Other: Torque constant 11 kg·cm/A (12 V) and 7.8 kg·cm/A (7.4 V) per Waveshare (unconfirmed)

Good for

Builders of Waveshare robots who want direct replacements, and anyone wanting an STS3215-class servo with English documentation and a web control demo.

Not good for

Buyers who need a guaranteed gear ratio match for SO-101 leader arms, since Waveshare does not publish ST3215 ratios.

Robots in the guide that use it

Waveshare RoArm-M3$239.99 – $339.99

Used across Waveshare's own robots and pan-tilt kits. Waveshare's bus-servo driver board is also the board recommended in the SO-101 build.

Sources Waveshare ST3215 wiki ↗ · Waveshare ST3215 store page ↗ · Waveshare ST3215-HS store page ↗ · Waveshare ST3235 store page ↗ · Waveshare ST3235 wiki ↗ · RoArm-M3 wiki (servo FAQ) ↗
Buying Waveshare ships from China (the store warned of a pause on October 1–4, 2026 for the National Day holiday). Waveshare products are also sold on Amazon US. Delivery time to the US is unconfirmed.

Feetech SCS0009

Feetech (Shenzhen FEETECH RC Model, China) · Available · $9.00

Seeed Studio, $9.00 each or $8.00 at 10+, October 2026 check. Robotopian from $15. AliExpress around $9–17 (unconfirmed).

The SCS0009 is Feetech's micro bus servo, about the size of a 9 g hobby servo but daisy-chained on the same serial bus as the bigger STS parts. Its low price made it the default for open-source dexterous hands such as AmazingHand. Feetech's STS3032 (4.5 kg·cm at 6 V, 32 × 12 × 27.5 mm, 20.6 g, 12-bit magnetic encoder, coreless motor, aluminum case, about $33–44 at US resellers (unconfirmed)) is the stronger step up in a similar slim format.

Torque: 0.23 N·m (2.3 kg·cm) stall, 0.07 N·m (0.7 kg·cm) rated at 6 V
Speed: 0.10 s/60° (about 100 rpm) no load at 6 V
Weight: 13.2 g
Size: 23.2 × 12.1 × 25.25 mm
Voltage: 4–7.4 V
Current: 150 mA no load, 1.0 A stall at 6 V
Gearing: 1:416 (per Seeed), copper and steel gears
Motor: Iron-core DC
Feedback: Potentiometer per Feetech's page (Seeed's listing calls it a 10-bit magnetic sensor), 0.293° per step over 300°. Reports position, speed, load, input voltage and temperature
Interface: TTL half-duplex serial bus, 38,400 bps – 1 Mbps, IDs 0–253, Feetech SCS protocol
Range: 300° position range (0–1023), no mechanical stop
Other: 20T output spline, PC plastic case, no ball bearing

Good for

Robot hands, grippers and tiny bus-servo robots where 9 g-class size matters and readback beats PWM guesswork.

Not good for

Legs or arm joints carrying real load, since 2.3 kg·cm is micro-servo torque and the 300° range rules out full rotation.

Pollen Robotics' open-source AmazingHand uses eight (two per finger). Seeed also lists it for Hugging Face's HopeJR hand.

Sources Feetech SCS0009 spec page ↗ · Seeed Studio SCS0009 ↗ · Seeed AmazingHand wiki ↗ · Feetech STS3032-C036 spec page ↗
Buying Seeed Studio ships this item from its China warehouse only. AliExpress 1–3 weeks (unconfirmed).

Feetech SM series (SM45BL, SM85CL)

Feetech (Shenzhen FEETECH RC Model, China) · Available · $141 (SM45BL), $212 (SM85CL) at US resellers

Robotopian lists the SM45BL-C001 from $141 and AIFITLAB the SM85CL-C001 from $212, October 2026 check. Chinese marketplace quotes are far lower (unconfirmed), so prices vary widely.

The SM line is Feetech's industrial-style family, which moves the bus to differential RS-485 and adds brushless or coreless motors in aluminum cases. The 24 V SM45BL packs 45 kg·cm into a body only slightly larger than an STS3215, and the 12 V SM85CL reaches 85 kg·cm. Feetech also sells larger SM units up to the 260 kg·cm SM-260B, plus Modbus-RTU versions for PLC-style integration.

Torque: SM45BL: 4.41 N·m (45 kg·cm) stall, 1.47 N·m (15 kg·cm) rated at 24 V. SM85CL: 8.34 N·m (85 kg·cm) stall, 2.75 N·m (28 kg·cm) rated at 12 V
Speed: SM45BL: 0.142 s/60° (70 rpm) no load at 24 V. SM85CL: 0.27 s/60° (37 rpm) no load at 12 V
Weight: SM45BL 100 g. SM85CL 215 g
Size: SM45BL 46.5 × 28.5 × 34 mm. SM85CL 62 × 34 × 47 mm
Voltage: SM45BL 24 V. SM85CL 12 V
Current: SM45BL 160 mA no load, 2.3 A stall at 24 V. SM85CL 200 mA no load, 3.2 A stall at 12 V
Gearing: Steel gears, SM45BL 353:1
Motor: SM45BL brushless. SM85CL coreless
Feedback: 12-bit magnetic encoder (4096 steps). Reports position, speed, voltage, load and temperature
Interface: RS-485 half-duplex serial bus, 38,400 bps – 1 Mbps, IDs 0–253. Modbus-RTU variants exist
Range: 360° position mode, motor (wheel) mode, no mechanical limit
Other: Aluminum cases, two ball bearings

Good for

Bigger desktop arms, grippers and robot joints that need several times the torque of an STS3215 and the noise immunity of RS-485 over longer cables.

Not good for

Small battery robots, since they need 12 V or 24 V supplies and an RS-485 adapter, and US retail prices are high next to TTL servos.

Sources Feetech SM-45BL-C001 spec page ↗ · Feetech SM-85CL-C001 spec page ↗ · Feetech serial bus servo catalog ↗
Buying Mostly sold through Chinese marketplaces (AliExpress, Alibaba) shipping from China, and small US resellers (Robotopian, AIFITLAB) whose shipping terms are unconfirmed.

Hiwonder LX-16A

Hiwonder (Shenzhen, China) · Available · $16.99

Hiwonder official store $16.99, October 2026 check. Also stocked by Micro Center and RobotShop (prices unconfirmed).

The LX-16A is Hiwonder's best-known standard-size bus servo and the template for its later LX, HX and HTD families. It uses a potentiometer rather than a magnetic encoder, and its protocol is private, so it needs Hiwonder's TTL/USB debug board or a compatible half-duplex circuit. Angle readback lets owners move joints by hand and record poses in Hiwonder's PC software.

Torque: 1.67 N·m (17 kg·cm) at 6 V, 1.96 N·m (20 kg·cm) at 7.4 V
Speed: 0.19 s/60° (about 53 rpm) no load at 7.4 V
Weight: 53–54 g
Size: 45.22 × 24.72 × 36.3 mm
Voltage: 6–8.4 V
Current: 100 mA no load, 1.1–1.9 A stall
Gearing: Full metal gears
Feedback: Potentiometer, 0.3° accuracy. Reports position, temperature and voltage
Interface: Hiwonder's own UART serial bus protocol at 115,200 bps, IDs 0–253
Range: 0–240° servo mode, continuous gear-motor mode
Other: LED status light, stall and over-temperature protection, settings saved at power-off

Good for

Budget DIY arms and hexapods that want daisy-chained wiring and angle readback for pose teaching.

Not good for

Full-rotation joints or high-accuracy work, since the potentiometer limits it to 240° and the protocol is Hiwonder-only.

A long-time favorite for DIY hexapods and arms built around Hiwonder's bus-servo boards.

Sources Hiwonder LX-16A product page ↗
Buying Hiwonder's store offers free US delivery on orders over $499, and the item is also stocked by Micro Center and RobotShop. Hiwonder's dispatch location and transit time are unconfirmed.

Hiwonder LX-224HV (and LX-224)

Hiwonder (Shenzhen, China) · Available · $19.99 (LX-224HV), $15.99 (LX-224)

Hiwonder official store, October 2026 check.

The LX-224HV is the 11.1 V version of Hiwonder's LX-224, and Hiwonder says the higher voltage cuts current by more than 60% compared with a 7.4 V servo, which matters with 18 servos on one battery. Three connectors on each servo make star or chain wiring easy inside a hexapod body. It is the leg servo in SpiderPi and SpiderPi Pro.

Torque: LX-224HV: 1.96 N·m (20 kg·cm) at 11.1 V. LX-224: 1.96 N·m (20 kg·cm) at 7.4 V
Speed: LX-224HV: 0.18 s/60° (about 56 rpm) no load at 11.1 V. LX-224: 0.20 s/60° (50 rpm) at 7.4 V
Weight: LX-224HV 62 g. LX-224 63 g
Size: 40 × 20.14 × 51.1 mm
Voltage: LX-224HV 9–12.6 V (11.1 V nominal). LX-224 6–8.4 V
Current: LX-224HV 100 mA no load, 1.7–2 A stall. LX-224 100 mA no load, 2.4–3 A stall
Gearing: Metal gears
Feedback: Potentiometer, 0.24° accuracy on the LX-224HV (0.3° on the LX-224). Reports position, temperature and voltage
Interface: Hiwonder UART serial bus at 115,200 bps, IDs 0–253, three connectors per servo
Range: 0–240° servo mode (0–1000 command range), 360° gear-motor mode
Other: Stall and over-temperature protection, settings saved at power-off, double-shaft mounting

Good for

Hexapods and other many-joint robots running from a 3S pack, where higher voltage cuts bus current.

Not good for

Projects needing magnetic-encoder precision or 360° positioning.

Robots in the guide that use it

Hiwonder SpiderPi / SpiderPi Pro$479.99 – $1,039.99

Sources Hiwonder LX-224HV product page ↗ · Hiwonder LX-224 product page ↗ · Hiwonder SpiderPi product page ↗
Buying Hiwonder official store, free US delivery on orders over $499. Dispatch location and transit time unconfirmed.

Hiwonder HX-35H (and HX-35HM)

Hiwonder (Shenzhen, China) · 2022 · Available · $18.99 (HX-35H), $35.99 (HX-35HM)

Hiwonder official store, October 2026 check.

The HX-35H is Hiwonder's 2022 high-voltage 35 kg·cm bus servo in the common 45 × 24.7 × 35 mm body, and it drives all 18 legs of JetHexa and JetHexa2027. The HX-35HM keeps the torque but swaps the potentiometer for a 12-bit magnetic encoder and a metal shell, extending range to 360° at the cost of 19 g more weight. AiNex mixes HX-35H, HX-35HM (at the hips) and smaller HX-12H servos.

Torque: 3.43 N·m (35 kg·cm) static maximum, 2.45 N·m (25 kg·cm) rotating at 11.1 V, same figures for HX-35H and HX-35HM
Speed: HX-35H 0.18 s/60° (about 56 rpm), HX-35HM 0.19 s/60° (about 53 rpm) no load at 11.1 V
Weight: HX-35H 52 g. HX-35HM 71 g
Size: 45.2 × 24.7 × 35 mm (both)
Voltage: 9–12.6 V
Current: 100 mA no load, 3 A stall
Gearing: Metal gears
Feedback: HX-35H potentiometer, 0.3° accuracy. HX-35HM 12-bit magnetic encoder (4096 steps), 0–1500 command range over 360°. Both report position, temperature and voltage
Interface: Hiwonder UART serial bus at 115,200 bps, IDs 0–253, 5264-3P connectors
Range: HX-35H 0–240° servo mode plus gear-motor mode. HX-35HM 0–360°
Other: HX-35HM has a CNC anodized aluminum shell

Good for

Mid-size legged robots on 3S batteries that need about twice the torque of 20 kg·cm servos at a low price.

Not good for

Joints that need full rotation or fine accuracy (on the potentiometer HX-35H), or any system expecting an open, industry-standard protocol.

Robots in the guide that use it

Hiwonder JetHexa$709.99 – $1,109.99

Hiwonder JetHexa2027$489.99 – $2,249.99

AiNex$730 – $1,040

Sources Hiwonder HX-35H product page ↗ · Hiwonder HX-35HM product page ↗ · Hiwonder AiNex product page (servo list) ↗ · Hiwonder JetHexa product page ↗
Buying Hiwonder official store, free US delivery on orders over $499. Dispatch location and transit time unconfirmed.

Lynxmotion Smart Servo (LSS) ST1 / HS1 / HT1

Lynxmotion (RobotShop, Canada) · Available · about $79 – $121

RobotShop US, prices include US tariffs. Archived RobotShop pages from late 2025 show the LSS-HS1 at $91.84 and the LSS-HT1 at $121.24, both in stock. October 2026 search listings showed LSS-HS1 $78.84–$86.24, LSS-ST1 $79.26 and LSS-HT1 $113.94 (unconfirmed, RobotShop blocks automated checks).

Lynxmotion's Smart Servo is a modular servo designed around its Servo Erector Set brackets, with a readable ASCII-style protocol rather than binary packets. Three variants share one case, mounting pattern and spline and trade speed for torque by gear ratio, and the HT1 adds a coreless motor, steel gears and an aluminum body. The full-duplex link and RC fallback make it easy to drive from almost any microcontroller, though a separate serial adapter is needed since none ships with the servo.

Torque: Static maximum at 12 V: HS1 0.78 N·m (8 kg·cm), ST1 1.37 N·m (14 kg·cm) (unconfirmed), HT1 2.84 N·m (29 kg·cm). Maximum dynamic torque is far lower, 1.6 kg·cm on the HS1 and 5.8 kg·cm on the HT1
Speed: No load at 12 V: HS1 100 rpm, ST1 60 rpm (unconfirmed), HT1 60 rpm
Weight: HS1 57 g, HT1 79 g (without horns). ST1 about 58 g (unconfirmed)
Size: 38.3 × 26 × 51 mm (unconfirmed)
Voltage: 6–12.6 V (12 V recommended)
Current: At 12 V, 70 mA no load standby on HS1 and HT1. Stall 300 mA (HS1) or 800 mA (HT1)
Gearing: HS1 1:146 copper gears. ST1 1:253 (unconfirmed). HT1 1:320 steel gears
Motor: Cored DC on HS1, coreless DC on HT1
Feedback: Position, speed, voltage, current and temperature
Interface: TTL full-duplex serial, 9,600–921,600 bps (115,200 recommended), Lynxmotion LSS protocol built on the SSC-32 command style, or standard RC PWM. Molex 4-pin 2.54 mm connector
Range: 360° absolute positioning, virtual multi-turn, continuous wheel mode
Other: RGB LED bar, 24T spline compatible with the Hitec standard, smart, wheel and RC modes. The HT1 now ships with a full aluminum body. Operating temperature 45–85 °C per RobotShop (HT1)

Good for

Modular builds with the Lynxmotion Servo Erector Set, and anyone who wants a smart servo that also accepts plain RC PWM.

Not good for

Budget multi-joint robots, since each servo costs several times an STS3215 with less torque.

Built into Lynxmotion's own SES-V2 kits, such as the 4-DoF robotic arm and the mechDOG quadruped (unconfirmed).

Sources Lynxmotion LSS specifications (wiki) ↗ · Lynxmotion LSS overview (wiki) ↗ · RobotShop LSS-HT1 ↗ · RobotShop LSS-HS1 ↗ · RobotShop LSS-ST1 ↗
Buying Sold by RobotShop, with shipping calculated at checkout. Warehouse location and transit time unconfirmed.

Kondo KRS-2552R3HV / KRS-2572R2HV ICS

Kondo Kagaku (Japan) · Available · about $53 (KRS-2552R3HV), about $77 (KRS-2572R2HV)

Converted from yen at about ¥158 per dollar, October 2026 check. Kondo's ROBOSPOT web shop lists the KRS-2552R3HV at ¥8,360 single or ¥40,480 for six, and the KRS-2572R2HV at ¥12,100 single or ¥60,500 for six, with all four listings out of stock at the time of checking. Kondo's product pages state open pricing.

The KRS-2552R3HV is the standard joint servo of the KHR-3HV Ver.3.1 kit, which ships with 17 of them. Kondo's ICS protocol lets the same servo run on serial or PWM, and version 3.6 added current-position readback. The KRS-2572R2HV fits the same case with a coreless motor and 25 kg·cm, and Kondo recommends it as a direct swap for KHR-3HV leg servos to improve stability.

Torque: KRS-2552R3HV 1.37 N·m (14.0 kg·cm) at 11.1 V. KRS-2572R2HV 2.45 N·m (25.0 kg·cm) at 11.1 V
Speed: KRS-2552R3HV 0.14 s/60° (about 71 rpm) at 11.1 V. KRS-2572R2HV 0.13 s/60° (about 77 rpm) at 11.1 V
Weight: KRS-2552R3HV 41.5 g. KRS-2572R2HV 47.7 g
Size: 41 × 21 × 30.5 mm (excluding protrusions)
Voltage: 9–12 V (HV)
Current: Max 1.3 A (KRS-2552R3HV), 2.5 A (KRS-2572R2HV)
Gearing: KRS-2552R3HV 312.4:1 all-metal gears. KRS-2572R2HV 309.11:1 special aluminum gears. Output shaft on a bearing
Motor: KRS-2572R2HV coreless
Feedback: Current position readback (ICS 3.6)
Interface: Kondo ICS 3.6, TTL serial at 115,200 / 625,000 / 1,250,000 bps, or PWM, selectable. Two ZH connectors for daisy-chaining
Range: 270° max operating angle, continuous rotation mode
Other: Resin case (glass-filled on 2572R2HV). Made in Japan

Good for

Kondo humanoids and ROBO-ONE style bipeds, where the slim 2500 case and drop-in torque upgrades matter.

Not good for

Builders outside Japan on a budget, since English documentation is thin and prices are high compared with Chinese bus servos.

Robots in the guide that use it

KHR-3HV¥136,400 (Japan)

KRS-2500 servos are a common choice in ROBO-ONE contest humanoids built from Kondo parts (unconfirmed).

Sources Kondo KRS-2552R3HV ICS product page ↗ · Kondo KRS-2572R2HV ICS product page ↗ · Kondo KHR-3HV Ver.3.1 product page ↗ · Kondo ROBOSPOT web shop (KRS-2552R3HV listings) ↗
Buying Sold mainly through Japanese retailers (Kondo ROBOSPOT, Vstone, Marutsu, Amazon Japan). US availability and shipping are unconfirmed.

Kondo KRS-3304R2 ICS

Kondo Kagaku (Japan) · Available · about $61

¥9,680 single at Kondo's ROBOSPOT web shop (in stock) and at Vstone, ¥51,480 for six, converted at about ¥158 per dollar, October 2026 check.

The KRS-3304R2 is Kondo's cube-type small servo with a coreless motor, giving near standard-size torque in a 32.5 × 26 × 26 mm body. The R2 revision moved to ICS 3.6 for position readback while keeping the KRS-3304's case, gears and motor. Kondo also sells the KRS-3304R2T1, a high-speed variant with 145.10:1 gearing and 0.06 s/60° at 7.4 V, as an in-house test-production item.

Torque: 1.36 N·m (13.9 kg·cm) at 7.4 V, 1.10 N·m (11.2 kg·cm) at 6.0 V
Speed: 0.11 s/60° (about 91 rpm) at 7.4 V, 0.13 s/60° at 6.0 V
Weight: 33.7 g
Size: 32.5 × 26 × 26 mm (excluding protrusions)
Voltage: 6–7.4 V
Gearing: 289.22:1 all-metal gears, bearing-supported shaft
Motor: Coreless
Feedback: Current position readback (ICS 3.6)
Interface: Kondo ICS 3.6, TTL serial at 115,200 / 625,000 / 1,250,000 bps, or PWM, selectable. Detachable cables with ZH connectors
Range: 270° (±135°), continuous rotation mode
Other: Cube-shaped resin case. Made in Japan

Good for

Compact humanoids and small walkers that want strong torque in a cube case that fits any orientation.

Not good for

High-voltage builds, since it is a 6–7.4 V part and cannot share a bus supply with Kondo HV servos.

Sources Kondo ROBOSPOT web shop (KRS-3304R2 listings) ↗ · Vstone KRS-3304R2 ICS product page (full specs) ↗ · Kondo KRS-3304R2T1 ICS product page ↗ · Kondo KRS series catalog ↗
Buying Japanese retailers (Kondo ROBOSPOT, Vstone, Kyoritsu Eleshop, Amazon Japan). Vstone lists it as a maker-stock item shipping in 2–3 business days within Japan. US shipping unconfirmed.

HerkuleX DRS-0101 (and DRS-0201)

Dongbu Robot (South Korea) · Available · $61.00

DFRobot $61.00 for the DRS-0101 and $158.00 for the metal-geared DRS-0201 (only 10 left), October 2026 check. RobotShop also lists both at about $76 and $170 (unconfirmed).

Dongbu Robot's HerkuleX servos were an early-2010s Korean rival to Dynamixel, with trapezoidal velocity profiles and torque limiting built into the servo. The DRS-0101 is the plastic-geared entry model, and the DRS-0201 is the 24 kg·cm metal-geared, coreless-motor sibling in the same case.

Torque: DRS-0101 1.18 N·m (12 kg·cm) stall at 7.4 V. DRS-0201 2.35 N·m (24 kg·cm) stall at 7.4 V
Speed: DRS-0101 0.166 s/60° (about 60 rpm) no load at 7.4 V. DRS-0201 0.147 s/60° (about 68 rpm) at 7.4 V
Weight: DRS-0101 45 g. DRS-0201 60 g
Size: 45 × 24 × 31 mm
Voltage: 7–12 V (optimized for 7.4 V)
Current: 450 mA rated at 7.4 V with 1.7 kg·cm load (DRS-0101)
Gearing: 1:266. Super engineering plastic on the DRS-0101, heavy-duty metal on the DRS-0201
Motor: Brushed cored DC on the DRS-0101, metal-brush coreless DC on the DRS-0201
Feedback: Position (0.325° resolution), speed, temperature, load, voltage
Interface: Full-duplex asynchronous serial (TTL), binary packets, multi-drop, IDs 0–253, up to 0.67 Mbps
Range: 320° position range, continuous rotation
Other: Built-in PID, feedforward, trapezoidal velocity profiles, torque saturation and overload protection

Good for

Maintaining older HerkuleX-based robots, and projects that want built-in motion profiling and diagnostics on a full-duplex link.

Not good for

New designs, since the line has seen little development in years and costs far more than modern Chinese bus servos with magnetic encoders.

LuxAI's QTrobot has used HerkuleX servos for its eight head and arm joints, though LuxAI's software now also supports Feetech servos and the exact model is unconfirmed.

Sources DFRobot DRS-0101 wiki (specs) ↗ · DFRobot DRS-0101 store page ↗ · DFRobot DRS-0201 store page ↗
Buying DFRobot ships from China (it paused shipping September 30 to October 7, 2026 for the National Day holiday). RobotShop also lists the servos for US buyers. Transit times unconfirmed.