SO-101
Low-cost 3D-printed arm sold as a leader–follower pair for teleoperation, built to work with the LeRobot library.
Project documentation
Before you build
Five answers, each linked to its source
What does it cost?
$121.94per follower arm
One follower arm at US prices. The leader + follower teleoperation pair is $229.88 (€226.30). Maker’s BOM table
Can I sell what I build?
YesCommercial use OK
Hardware Apache-2.0 · Software Apache-2.0. Licensing source
What’s open?
5 of 6CAD: AvailableBOM: AvailablePCB: Off-the-shelf partCode: AvailableSim: AvailableGuide: Available
PCB off-the-shelf. All six files
Is it maintained?
Active
Latest activity Oct 6, 2026 · 15 commits in the last 52 weeks · 40 contributors Activity
01 / Under the shell
The specifications.
Hardware, build and software on one sheet. Every fact links to where we found it.
A low-cost, 3D-printed robot arm designed by TheRobotStudio in collaboration with Hugging Face. It is built as a leader–follower pair for teleoperation and is designed to work with the open-source LeRobot library. SO-101 succeeds the SO-100 with improved wiring, easier assembly and updated leader-arm motors.
Hardware
- Actuators
- 6 · STS3215 servos README
- Build
- 3D-printed · PLA+ · FDM Documentation
- Actuated joints
- 6: five arm joints plus the gripper URDF
- Servos
- Feetech STS3215, 7.4 V (12 V high-torque option) README
- Stall torque
- 16.5 kg·cm at 6 V (7.4 V version) · 30 kg·cm (12 V version) README
- Controller
- Waveshare serial bus servo driver over USB-C README
- Material
- PLA+ on a hobby FDM printer README
- Previous version
- SO-100 (its docs are now deprecated) README
Building it
- Printer
- FDM with a 0.4 mm nozzle at 0.2 mm layers (or 0.6 mm at 0.4 mm), 15% infill, supports on README
- Bed size
- Single-plate files for 220 × 220 mm (Ender) and 205 × 250 mm (Prusa) beds README
- Fit check
- Printable gauges test tolerance against an STS3215 servo or a Lego brick README
- Tools
- Phillips #0 and #1 screwdrivers README
Software & simulation
- LeRobot
- Designed to work with Hugging Face’s open-source LeRobot library; setup tutorial in its docs README
- MuJoCo
- MJCF model and scene in Simulation/SO101 Repo files
- URDF
- Calibrated URDFs for the follower and leader arms Repo files
02 / The files behind the robot
What’s open.
Six parts of the build, each checked separately. Gaps stay visible.
| Part | Status | What’s there | License | Source |
|---|---|---|---|---|
| CAD | Available | STEP and STL for every part (36 STEP, 117 STL), plus single-plate print files | Apache-2.0 | Repo files |
| Bill of materials | Available | Priced parts table with buy links for the US, EU, China and Japan | Apache-2.0 | README |
| Electronics | Off-the-shelf part | Off-the-shelf Waveshare servo driver board; no custom PCB needed | — | README |
| Code | Available | Runs on Hugging Face LeRobot | Apache-2.0 | LeRobot |
| Simulation model | Available | URDF and a MuJoCo MJCF scene | Apache-2.0 | Simulation/SO101 |
| Assembly guide | Available | Step-by-step guide in the LeRobot docs | Not documented | LeRobot docs |
03 / Know before you build
Can you sell it?
YesCommercial use OK
The whole repository, CAD files included, is Apache-2.0. You can build, modify and sell robots based on it, as long as you keep the license and copyright notices.
- Hardware
- Apache-2.0
- Software
- Apache-2.0
04 / The upstream project
Is it maintained?
ActiveLatest activity Oct 6, 2026, 15 days before the snapshot
- Stars
- 7,831
- Forks
- 722
- Contributors
- 40
- Latest release
- v0.1.1 · May 17, 2024
Snapshot captured Oct 21, 2026. Recorded figures, not live metrics. Active: activity within 90 days of the snapshot. Quiet: within a year. Dormant: longer.
05 / Parts & kits
A head start.
9 sellers listed by the maker. No affiliate links or paid placement.
MAKER’S COST
$121.94
per follower arm
One follower arm at US prices. The leader + follower teleoperation pair is $229.88 (€226.30).
Maker’s BOM table06 / Side by side
Compare with other arms.
The three arms with the closest documented maker’s cost. Same sources, same rules.
| Robot | Cost | Open files | Can I sell it? | Runs on | Maintained | Stars |
|---|---|---|---|---|---|---|
| SO-101This robotTheRobotStudio × Hugging Face | $121.94per follower arm | 5 of 6 | YesHW Apache-2.0 · SW Apache-2.0 | LeRobotMuJoCo | ActiveOct 6, 2026 | 7,831 |
| Mini-ArmJonathan Shulgach | About $82Basic build | 5 of 6 | YesHW MPL-2.0 · SW Mozilla Public License 2.0 | ROS 2Raspberry PiPython | ActiveOct 23, 2026 | 14 |
| AM-ARM200Li Yiteng and Wu Zhiyong | $243.33follower arm BOM | 4 of 6 | YesHW Apache-2.0 · SW Apache-2.0 | LeRobot | QuietJun 18, 2026 | 90 |
| PingTi Armnomorewzx | About $261single PingTi arm | 4 of 6 | YesHW Apache-2.0 · SW Apache-2.0 | LeRobot | ActiveOct 20, 2026 | 55 |
| This robotSO-101 | Mini-Arm | AM-ARM200 |
|---|---|---|
| Cost | ||
| $121.94 | About $82 | $243.33 |
| Can I sell it? | ||
| Yes | Yes | Yes |
| Open files | ||
| 5 of 6 | 5 of 6 | 4 of 6 |
| Runs on | ||
| LeRobot, MuJoCo | ROS 2, Raspberry Pi, Python | LeRobot |
| Maintained | ||
| ActiveOct 6, 2026 | ActiveOct 23, 2026 | QuietJun 18, 2026 |
Upkeep is measured against each robot’s own snapshot. Costs keep the maker’s scope, so check what each figure covers.
See them in the tableConnected projects and guides
Keep exploring.
- PREVIOUS VERSIONSO-100 The original arm; SO-101 improves wiring and assembly
- BUILT ON ITXLeRobot Dual-arm mobile robot with 2 × SO-101 and a LeKiwi base, about $660 in parts
- ADD-ONAmazingHand A community interface mounts the AmazingHand on SO-Arm
- GUIDELeRobot SO-101 tutorial Assembly, setup and teleoperation
07 / Follow the evidence
Open books.
Repository files are pinned to commit a758567. Websites and papers are listed with their review dates.
- 01README at commit a758567Reviewed Oct 21, 2026
- 02LICENSE (Apache-2.0)Reviewed Oct 21, 2026
- 03Simulation/SO101/so101_new_calib.urdfReviewed Oct 21, 2026
- 04LeRobot SO-101 documentationReviewed Oct 21, 2026
- 05GitHub API: stars, contributors, commit activityReviewed Oct 21, 2026