SO-101

SO-101 is a low-cost, open-source 6-DOF robot arm and the flagship robot of the Hugging Face LeRobot ecosystem. It is based on TheRobotStudio's SO-ARM100 design and is mostly 3D-printed and assembled from off-the-shelf parts (with a public bill of materials).

The kit works in a leader-follower setup: an operator moves the leader arm and the follower arm mirrors the motion — enabling collection of demonstrations for imitation learning. The follower arm uses 6 Feetech STS3215 bus servos with 1/345 gearing, while the leader uses tuned gear ratios (1/191, 1/345, 1/147) so it can hold its own weight and be moved easily.

SO-101 integrates with the LeRobot library (configured and calibrated via the lerobot tools and the Feetech SDK). Thanks to its low cost and openness, it has become a popular platform for learning robotics, teleoperation, and training manipulation policies on real hardware.