SO-101 Robot Arm Kit: What It Costs, What to Buy and How to Set It Up

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The SO-101 is a low-cost, open-source robot arm made for learning robot AI with Hugging Face’s LeRobot library. The official SO-ARM100 repository lists electronics for a two-arm setup at $229.88 in US prices, or $121.94 for a single follower arm. Those totals do not include the 3D-printed body, cameras or a computer, so plan on more than the parts list if you buy a ready kit.

Most people buy two arms. You move the leader arm by hand, the follower arm copies it, and LeRobot records the camera images and joint positions as training data. A policy trained on that data then drives the follower on its own.

What is in an SO-101 setup

The design comes from The Robot Studio and Hugging Face and is published under the Apache 2.0 license. Each arm has six Feetech STS3215 serial bus servos: five joints plus the gripper on the follower, or a trigger handle on the leader. According to the LeRobot SO-101 assembly guide:

  • Follower arm: six STS3215 servos with 1/345 gearing.
  • Leader arm: one 1/345 servo, two 1/191 servos and three 1/147 servos. The lower gear ratios let the arm hold its own weight while staying easy to move by hand.
  • Per arm: one motor control board (Waveshare in the parts list), one power supply, a USB-C cable and a table clamp.

The SO-101 replaced the SO-100. The repository says the newer version has better wiring, uses different leader motors and no longer requires removing gears from the motors during assembly. The SO-100 documentation is now marked deprecated.

How much it costs

The official parts list gives these totals, with links to Alibaba, Amazon, TaoBao and Akizuki Denshi:

  • Leader and follower pair: $229.88 (US), €226.30 (EU), ¥1,343 (China), ¥44,530 (Japan)
  • One follower arm: $121.94 (US), €124.30 (EU), ¥682 (China), ¥24,414 (Japan)

The 12 servos make up most of that cost at $13.89 each in the US list. Prices in the repository are reference prices from the linked shops and change by country and date, so open the links before you budget.

Add these to the parts list:

  • 3D-printed parts: print them yourself in PLA+ at 15% infill, or buy a printed kit. The repository provides one-file prints for 220 × 220 mm and 205 × 250 mm beds and a page of printing services if you don’t own a printer.
  • Cameras: the parts list has none. Imitation learning needs at least one camera, and many setups add a wrist camera. The repository includes mounts for small UVC modules, RealSense D405 and D435 cameras and a webcam.
  • A computer for training: recording works on a laptop, but training policies is much faster on an NVIDIA GPU. For an on-robot computer, see our Jetson Orin Nano vs Orin NX guide.

Build from parts or buy a kit

The repository describes two routes. Building from parts costs least but takes the most time. Buying a kit trades money for time. The kit list in the repository names these sellers as of October 19, 2026:

  • Seeed Studio (international, China, Japan via Akizuki Denshi, AliExpress): kits with 3D-printed parts.
  • WowRobo (international, China): assembled versions.
  • PartaBot (US): assembled versions, plus LeKiwi and Koch robots.
  • ForgeMotion Labs (US, also on Amazon): printed frame kits, electronics kits and complete arm kits.
  • Robonine (international): parts kits.
  • RoboSEasy (South Korea, Naver Smart Store), NeoBot (China) and Autodiscovery (EU).

Kit contents differ a lot. Before you pay, check whether the listing includes both arms, all 12 servos with the correct gear ratios, printed parts, controller boards and power supplies, and whether it is assembled and calibrated. A “follower only” kit will not give you leader-arm teleoperation.

Pick the motor voltage before you order

The follower’s STS3215 servos come in two versions. The repository says the 7.4V version has a stall torque of 16.5 kg·cm at 6V, a little less on the 5V supply in the parts list. The 12V version has 30 kg·cm, but then you need a 12V supply rated at 5A or more instead of the 5V one. The leader arm always uses 7.4V servos.

The project team says the 7.4V version was enough in its own use. Choose 12V if you plan to lift heavier objects or want more holding force, and make sure the kit seller ships the matching power supply.

Setting it up with LeRobot

After the arms are built, the software steps follow the official guide:

  1. Install LeRobot and the Feetech extra with pip install -e ".[feetech]".
  2. Run lerobot-find-port to find which USB port belongs to each arm’s control board.
  3. Run lerobot-setup-motors for the follower and then the leader. The script asks you to connect one motor at a time and writes a unique ID and baud rate to each. Do this before you chain the motors together.
  4. Assemble the joints in order. The guide has a short video for each joint and lists the M2×6 and M3×6 screws needed. Phillips #0 and #1 drivers fit all of them.
  5. Run lerobot-calibrate for each arm: move every joint to the middle of its range, press Enter, then move each joint through its full range.
  6. Start teleoperation and record demonstrations.

Calibration matters more than it looks. It makes the leader and follower report the same values for the same pose, and it lets a policy trained on one SO-101 work on another. Our LeRobot getting-started guide covers datasets, recording and training after this point.

Is the SO-101 the right first arm?

It fits well if you want to learn imitation learning and VLA models on real hardware for a few hundred dollars. LeRobot supports SO-101 data with policies such as ACT, SmolVLA and π0, so you can follow published tutorials without writing drivers.

It is a small hobby-grade arm, not an industrial one. The plastic body and hobby servos limit payload, precision and duty cycle, and the arm has no safety-rated stop. Clamp it to a table and keep hands clear of the follower while a policy runs. If you need payload and repeatability for real work, look at commercial collaborative arms; our guide to cobot total cost explains what those quotes include.