robotindex SO-101
A 3D-printed, 6-joint desktop robot arm designed by The Robot Studio in collaboration with Hugging Face, built around low-cost Feetech bus servos. Used in matched leader/follower pairs for teleoperated imitation-learning research — a human demonstrates a task by hand-guiding the leader arm while the follower's motions and camera feed are logged as training data. The current flagship of this arm family, directly succeeding SO-100: the leader arm now ships with naturally lower-torque, factory-backdrivable servo variants, eliminating SO-100's gear-pulling modification entirely.
huggingface.co/docs/lerobot/so101 →
Image: user-submitted
Specs
Weight
Not publishedno official figure found in this research
Software
Hugging Face
lerobotApache-2.0; trains ACT, SmolVLA, and other imitation-learning policiesDegrees of Freedom
6 total5 arm joints (base, shoulder, elbow, wrist pitch, wrist roll) + 1 gripper axis
Payload
~500g (est.)third-party estimate — no official payload, reach, or repeatability spec published
Actuators
Feetech STS3215follower keeps standard 1/345 gearing (or a 12V/30kg·cm "Pro" variant); leader uses factory lower-torque ratios instead — no more gear-pulling
Status
Current flagshipsupersedes SO-100, whose own docs are now marked deprecated
Construction
FDM 3D-printedPLA/PLA+; individual per-part STL files (vs. SO-100's print trays); revised wiring addresses a joint-3 disconnection issue
Teleop Method
Leader/follower pairleader ships naturally backdrivable out of the box — no servo disassembly needed, unlike SO-100
Host Interface
Waveshare Bus Servo Adapterrequired USB-C-to-servo-bus board, visible at this arm's base; needs its own separate DC power input
Creator
The Robot StudioRob Knight; kit manufacturing now also involves Seeed Studio, WowRobo, and PartaBot
Reference Price
Pricing is essentially unchanged from SO-100: the project's own bill-of-materials still prices a complete leader+follower teleoperation pair at roughly $230 in parts, while Seeed Studio sells electronics-only kits at $220 for the standard version or $240 for a "Pro" variant. Fully assembled kits from resellers are reported anywhere from roughly $100 to $500 depending on assembly level and shipping/tariffs — a wide range that isn't consistently corroborated across sources, so treat the top end cautiously.
Insights
SO-101 isn't a Hugging Face design any more than SO-100 was — both come from Rob Knight of The Robot Studio, with Hugging Face's role limited to software integration via its
lerobot library, not the hardware itself. Reach and payload figures commonly quoted around 500mm and 500g are third-party estimates only; neither Hugging Face nor the GitHub repo publishes official reach, payload, or repeatability figures for SO-100 or SO-101.Firmware & Community
TheRobotStudio/SO-ARM100
Open hardware and software repo — SO-101 is the direct successor to SO-100 in the same LeRobot-native lineage. Community teleoperation calibration presets for both arms are also listed in Builds & Mods.
LeRobot Teleoperation Calibration Presets
Community-shared calibration presets for teleoperating and training SO-100/SO-101 arms with Hugging Face LeRobot.
Specs compiled from the official TheRobotStudio/SO-ARM100 GitHub repository (including its README, BOM tables, per-model STL folders, and LICENSE file), Hugging Face's official LeRobot documentation for SO-101, Seeed Studio's kit listings, and independent coverage (TechCrunch, ThinkRobotics, OpenELAB, DeepWiki) as of this build. SO-101 supersedes SO-100 directly, so this page replaces what was previously this catalog's standalone SO-100 entry — SO-100 is now described here as SO-101's predecessor. Exact per-joint leader-servo gear ratios and reach/payload figures vary slightly or are unofficial across sources; see Worth Knowing above for specifics. Pricing varies by sourcing method (raw BOM vs. assembled kit) — see Reference Price above.