SO-101 arm: kit or assembled, 7.4 V or 12 V
You make two choices when you buy an SO-101 follower arm. This page tells you which one fits your work, and what you still need after the box arrives.
Short answer. Buy the 12 V servos if the arm will lift things for a policy you train. Buy 7.4 V if cost matters most and the loads are light. Buy the kit if you want to know every joint. Buy it assembled if you want to record data on the first day.
The four versions
| Version | Servos | Price | Good for |
|---|---|---|---|
| Kit, 7.4 V | 6 × STS3215, 19.5 kg·cm | €279 | Learning, light objects, lowest cost |
| Kit, 12 V | 6 × STS3215, 30 kg·cm | €299 | You build it, and you want the stronger arm |
| Assembled, 7.4 V | 6 × STS3215, 19.5 kg·cm | €349 | Teaching and demos, no build time |
| Assembled, 12 V | 6 × STS3215, 30 kg·cm | €369 | Research data from the first day |
Prices include VAT. Shipping is extra: Hungary €5, most of Europe €15, rest of the EU €20. We ship in the EU only.
Kit or assembled
The two contain the same parts. The difference is €70 and who does the build.
The kit
- The printed parts are in the box. You do not need a 3D printer.
- You do not solder. You screw it together and plug in the cables.
- Plan an evening. Follow the Hugging Face SO-101 assembly guide. It has a short video for each joint.
- The build teaches you where each servo sits. That helps when you replace one later.
Assembled
- We build it in Budapest. We move each joint through its range before we pack it.
- You run LeRobot's calibration once on your computer. Then the arm is ready.
- Choose this for a class, a lab bench or a demo, where build time costs more than €70.
7.4 V or 12 V
Both versions use six Feetech STS3215 servos. The 12 V servos give 30 kg·cm. The 7.4 V servos give 19.5 kg·cm. The 12 V arm costs €20 more.
- Choose 12 V for heavier objects, or for work at full reach, where the shoulder and elbow carry the most load. More torque gives more margin before a servo stalls.
- Choose 7.4 V for light objects — blocks, cups, pens — and for a first arm on a tight budget.
- Match the power supply to the servos. A mains supply is not in the box. A 12 V supply on 7.4 V servos can damage them. Label the supply if you keep both on one bench.
The software is the same for both. LeRobot drives the 7.4 V and the
12 V follower with the same so101_follower robot type.
What is in the box
- Six STS3215 servos (12 V or 7.4 V, as you chose)
- The printed parts
- The driver board
- Cables and screws
- A table clamp
Not in the box: a mains power supply, a camera and a leader arm.
Do you need a leader arm?
We sell the follower — the arm that does the work. The leader is the arm you move by hand to teach it. LeRobot copies the leader's pose to the follower, and records both to make a training dataset.
- To record demonstrations by hand, you need a leader arm. It is a separate SO-101 build with its own board and supply. The open design is in TheRobotStudio's SO-ARM100 repository.
- To run a trained policy, or to drive the arm from Python, you need only the follower.
Buying for a university or a company
Use Invoice an institution on the shop page. Outside Hungary, give us your VAT number and the invoice has no VAT. We reply with an invoice.
Every order has a 14-day cancellation from delivery and the 2-year legal guarantee. See the refund policy and the terms.
SO-101 is an open-source arm design by TheRobotStudio and Hugging Face. LeRobot is Hugging Face's open-source robot learning library. Komatachi is not affiliated with either.