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Build the $100-class SO-101 open-source robot arm: media published by TheRobotStudio/SO-ARM100
Demo video on YouTube (opens in a new tab)Credit: TheRobotStudio/SO-ARM100
Build the $100-class SO-101 open-source robot arm: media published by TheRobotStudio/SO-ARM100 (image 2)
Build the $100-class SO-101 open-source robot arm: media published by TheRobotStudio/SO-ARM100 (image 3)

Build the $100-class SO-101 open-source robot arm

Arm, Medium, $122, 2-4 h assembly

One SO-101 follower arm is $121.94 in US parts per The Robot Studio BOM (pair $229.88). 3D-print the frame, buy Feetech STS3215 servos and a motor board, then run it with Hugging Face's LeRobot.

Cost $122: SO-ARM100 README BOM, per arm. Build time 2-4 h assembly: SO-ARM100 README.

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Start with the follower BOM if you only need one arm for scripts or an agent. Add the leader arm when you want teleoperation. SO-101 improves wiring over SO-100 and uses geared servos tuned for leader vs follower. The repo has STLs, US/EU/CN/JP buy links, assembly guides and a URDF.

Does it work: yes with LeRobot. The Robot Studio README says the arms are designed to work with Hugging Face's LeRobot for teleop, recording and training. Seeed Studio, WowRobo and others sell printed or assembled kits listed on the same page.

Hardware & cost: Feetech STS3215 servos, a motor control board, power supply, clamps and printed parts. README BOM totals $121.94 per follower arm and $229.88 for a leader + follower pair (US, checked Nov 3, 2026). Printed parts, shipping and tax are extra.

Difficulty: Medium. Printing plus about 2-4 hours of assembly; no soldering.

Next step: open the SO-ARM100 repo, order the follower parts for your region, print the frame, then follow the LeRobot SO-101 setup to find ports and calibrate.

Agent install prompt (paste into Claude Code, Cursor or Codex): "Open https://github.com/TheRobotStudio/SO-ARM100, list the SO-101 parts I still need with buy links for the US, then set up LeRobot (`pip install lerobot`) and walk me through finding ports and calibrating the follower and leader arms."

Source: TheRobotStudio/SO-ARM100 on GitHub — https://github.com/TheRobotStudio/SO-ARM100 (facts checked against the project README, Nov 3, 2026; prices vary by region).

Quick answers

How much does it cost to build the $100-class SO-101 open-source robot arm?
About $122, per the SO-ARM100 README BOM, per arm.
How long does it take to build the $100-class SO-101 open-source robot arm?
2-4 h assembly, per the SO-ARM100 README.
What do you need to build the $100-class SO-101 open-source robot arm?
Feetech STS3215 servos, a motor control board, power supply, clamps and printed parts. README BOM totals $121.94 per follower arm and $229.88 for a leader + follower pair (US, checked Nov 3, 2026). Printed parts, shipping and tax are extra.

Buying the parts new, one SO-101 follower arm came to $131.69 at Oct 30 retail prices. See the SO-101 parts list and cost.

Interfaces

Parts list

Some buy links may earn Robot Use Cases a commission. You pay the same price. Prices are what the builder listed in their source, so check the store.

SO-101: one follower arm

Builder's listed total $121.94

Also needed: 3D-printed parts in PLA+ (or a printed kit below). Phillips #0 and #1 screwdrivers.

Or buy a kit

Kits listed in the SO-ARM100 README. Prices change by option, so check the vendor page.

From TheRobotStudio/SO-ARM100 README, Parts for One Follower Arm, checked 2026-10-17.

SO-101: leader + follower pair (for teleop and LeRobot training)

Builder's listed total $229.88

Also needed: 3D-printed parts for both arms in PLA+ (or a printed kit below). The leader's six servos are also sold as one bundle.

Or buy a kit

Kits listed in the SO-ARM100 README. Prices change by option, so check the vendor page.

From TheRobotStudio/SO-ARM100 README, Parts For Two Arms, checked 2026-10-17.

Ideas to try with it

Our ideas, not the builder's claims.

  1. Print the parts on a weekend and puppet the follower with the leader arm
  2. Use it as the arm for every LeRobot tutorial before buying anything bigger
  3. Mount a webcam and record your first dataset the same day
1 more idea
  1. Hand the joint controls to a coding agent and ask it to draw a circle
Source
TheRobotStudio/SO-ARM100 on GitHub
Last commit
2026-10-06
Builder
TheRobotStudio
Repo
TheRobotStudio/SO-ARM100, 7,975 stars
Built with
SO-100/SO-101 arm (LeRobot)

SO-101 / LeRobot, 4 builds: Build the $100-class SO-101 open-source robot arm · Run SmolVLA on an SO-101 so it follows plain-English tasks · Teach an SO-101 arm to pick and place with LeRobot · Livestream and remote-control your SO-101 arm from a web app

Parts notes for this device are in the Hermes Workshop catalog.

What to build next

Builds that share a board, robot or agent with this one.