What is the difference between SO-ARM100 and SO-101?

SO-101 is the current revision of the SO-ARM100: improved joint-3 wiring, optimized gear ratios, and the leader arm can also follow the follower for RL human-intervention. Both are 6-DOF, open-source (Apache-2.0), and natively supported by Hugging Face LeRobot.

How much is a SO-101 LeRobot arm?

The SO-101 servo kit starts around $199-$240; assembled leader+follower pairs run higher. It works out of the box with LeRobot.

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SO-ARM100 vs SO-101 — Which LeRobot Arm to Buy

The SO-ARM is the low-cost 6-DOF arm behind most Hugging Face LeRobot imitation-learning projects. SO-101 is the current revision. Here's what changed vs SO-ARM100 and which to buy.

SO-ARM100 vs SO-101

	SO-ARM100	SO-101 (current)
DOF	6 (5 + gripper)	6 (5 + gripper)
Kit price (from)	~$199	~$199–$240
Wiring	original	improved joint-3 wiring
Gears	original	optimized gear ratios
Teleop	leader → follower	leader can also follow (RL human-intervention)
LeRobot support	yes	yes (native)

Both are open-source (Apache-2.0, The Robot Studio) and sold as servo kits + 3D-printed parts or assembled pairs. Photo credit for SO-101: The Robot Studio.

Which should you buy?

New builds → SO-101: the wiring + gear fixes and leader-follow make it the better teleop/RL platform.
Existing SO-ARM100 users → no need to replace; SO-101 parts are largely compatible.
Pair it with a webcam + compute (Jetson/Pi) for a full LeRobot rig.

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