Guide · updated 2026-10-16
SO-101 vs SO-100
Buy the SO-101. The SO-100 docs are deprecated. The SO-101 is easier to assemble (no gear removal), has better wiring, and costs about $122 for one follower arm.
The SO-101 is the next-generation version of the SO-100 arm from The Robot Studio and Hugging Face. Per the official SO-ARM100 repo, it has improved wiring, is easier to assemble (no gear removal), and uses updated motors for the leader arm. The SO-100 docs are now marked deprecated.
| SO-100 | SO-101 | |
|---|---|---|
| Status | Deprecated docs | Current, recommended |
| Assembly | Requires removing gears for the leader | No gear removal |
| Wiring | Original | Improved routing |
| Leader-arm motors | STS3215 with gears removed | Mixed-ratio STS3215: 3× 1/147, 2× 1/191, 1× 1/345 |
| Follower-arm motors | 6× STS3215 | 6× STS3215 7.4V 1/345 (12V option for more torque) |
| BOM (US) | Similar | $121.94 one arm · $229.88 pair |
| LeRobot | Supported | Supported (reference arm) |
Which should you buy?
Buy the SO-101. It costs about the same, it's easier to build, and it's what current LeRobot tutorials, kits and community datasets assume. If you already own an SO-100, keep it: LeRobot still supports it, and the arms are mechanically close. For the full parts list and what each piece costs, see the SO-101 parts list and cost guide.
7.4V or 12V follower servos?
The README notes the 7.4V STS3215 has about 16.5 kg·cm stall torque at 6V, and the 12V version about 30 kg·cm. 7.4V is enough for most tabletop tasks; choose 12V for heavier objects.
What to build next
Once your arm is calibrated, try these SO-101 projects.
Common questions
Is the SO-100 obsolete?
Its docs are deprecated in favor of the SO-101, but LeRobot still supports SO-100 arms.
Are SO-100 and SO-101 parts compatible?
They share the STS3215 servos and most hardware, but SO-101 printed parts and leader-arm gearing differ. Follow one BOM for a build.
What to build next
Builds that share a board, robot or agent with this one.
Teach an SO-101 arm to pick and place with LeRobotAlso built on the SO-101 arm
Build the $100-class SO-101 open-source robot armAlso built on the SO-101 arm
Run SmolVLA on an SO-101 so it follows plain-English tasksAlso built on the SO-101 arm
Use a folding phone as a controller for an SO-101 gripperAlso built on the SO-101 arm
Livestream and remote-control your SO-101 arm from a web appAlso built on the SO-101 arm
Put an SO-101 arm on wheels with LeKiwiAlso built on the SO-101 arm
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