SO-101 (SO-ARM101) parts list
Low-cost 3D printed 6-DOF arm pair (leader plus follower) for teleoperation and imitation learning with LeRobot.
Robot armsbeginner by TheRobotStudio and Hugging Face
3D model: take it apart
Parts diagram
Tap any part to see where to buy it. Diagram is schematic, not to scale.
Every part you need
| Part | Qty | Spec | Where to buy |
|---|---|---|---|
| Feetech STS3215 7.4V, 1/345 gear (C001) follower arm servos + leader shoulder lift | 7 | 7.4V, 19.5 kg.cm stall at 7.4V; 6 for the follower, 1 for leader joint 2; official BOM lists $13.89/unit Highest torque 7.4V variant; carries the arm's load. | Seeed Studio: $20.00 OpenELAB: EUR 23.57 Akizuki Denshi: JPY 3,200.00 RobotShop: $34.32 Alibaba: check price (unverified) single; BOM link |
| Feetech STS3215 7.4V, 1/191 gear (C044) leader arm servos (base pan, elbow) | 2 | 7.4V, 27.4 kg.cm stall at 7.4V per vendor sheets; leader joints 1 and 3 Lower gearing so the leader moves by hand yet holds its own weight. | Seeed Studio: $21.99 OpenELAB: EUR 23.57 Akizuki Denshi: JPY 2,980.00 Alibaba: check price (unverified) single; BOM link |
| Feetech STS3215 7.4V, 1/147 gear (C046) leader arm servos (wrist flex, wrist roll, gripper) | 3 | 7.4V, 14.4 kg.cm stall at 7.4V; leader joints 4, 5 and 6 Lightest gearing so the wrist and trigger are easy to move by hand. | Seeed Studio: $20.00 OpenELAB: EUR 23.57 Akizuki Denshi: JPY 3,200.00 Alibaba: check price (unverified) single; BOM link |
| Waveshare Bus Servo Adapter (A) / Serial Bus Servo Driver Board servo bus controller | 2 | USB to TTL bus board with DC jack; Waveshare part 25514; official BOM lists $10.6/unit on Amazon Connects the servo chain to your computer over USB and feeds servo power. | Waveshare: $4.99 Amazon: check price Akizuki Denshi: JPY 1,280.00 The Pi Hut: GBP 4.80 (unverified) |
| USB-C cable, 2-pack USB cables | 1 | USB-A or USB-C to USB-C data cable One cable per controller board to the PC. | Amazon: check price |
| 5V power supply, 5.5x2.1 mm barrel servo power | 2 | 5V barrel supply as linked in the BOM; use a 12V 5A+ supply only if you buy 12V servos Powers the 7.4V STS3215 chain (5V is what the docs use). | Amazon: check price Amazon: check price |
| Table clamps 4-pack mounting | 1 | Small trigger or C clamps Holds the arm base to the desk so it does not tip. | Amazon: check price |
| Precision screwdriver set tools | 1 | Needs Phillips #0 and #1 The M2 and M3 screws use #0 and #1 heads. | Amazon: check price |
Quantities follow the official SO-101 (SO-ARM101) docs: https://huggingface.co/docs/lerobot/so101. "Unverified" prices come from search listings or older BOMs that we could not confirm on the seller's product page.
Kits (fewer orders, check what they leave out)
| Kit | Price | Includes | Leaves out | Buy |
|---|---|---|---|---|
| SO-ARM101 Pro Servo Motor Kit (no printed parts) Seeed Studio | $277.99 | Servos for leader and follower (12V follower in the Pro), adapter boards, cables per Seeed | 3D printed parts, camera; check power supplies on the page | Seeed Studio: $277.99 |
| SO-ARM101 Low-Cost AI Arm Servo Motor Kit (no printed parts) Seeed Studio | $240.00 | 7.4V servos for both arms, adapter boards, cables (price seen as an add-on on Seeed's LeKiwi page) | 3D printed parts ($29.90 add-on), camera | Seeed Studio: $240.00 |
| SO-101 leader servo bundle, 6 pcs Alibaba (official BOM footnote) | check price | All six leader servos: 3x C046 (1/147), 2x C044 (1/191), 1x C001 (1/345) | Follower servos, boards, power, printed parts | Alibaba (official BOM footnote): check price |
| SO-ARM101 DIY kit / assembled version WowRobo | check price | DIY or fully assembled options per the official kit list | Check the page; price not verified | WowRobo: check price |
| Assembled SO-101 arms (US) PartaBot | check price | Assembled arms per the official kit list | Store link only; product page and price not verified | PartaBot: check price |
3D printed parts
Needed. PLA+, 0.4 mm nozzle at 0.2 mm layers, 15% infill, supports on. Print the gauge files first to check servo fit. Single-plate files exist for Ender (220 mm) and Prusa (205x250 mm) beds. Files: https://github.com/TheRobotStudio/SO-ARM100/tree/main/STL/SO101
Mistakes builders make
- The leader needs three different gear ratios (1x 1/345, 2x 1/191, 3x 1/147). Buying 12 of the same servo gives a stiff leader that is hard to move by hand.
- SO-101 leader servos are always 7.4V. If you go 12V for the follower, you need a 12V 5A+ supply for that arm only.
- On the Waveshare board, set both jumpers to the B (USB) channel or the motor setup script cannot see the servos.
- Set motor IDs one servo at a time with only that servo connected; new servos all ship as ID 1.
- If a servo will not slide into the printed base, check printer calibration with the gauge prints; one builder found a part 2 mm undersized.
- Follower base and shoulder can buzz or vibrate; lowering the servo P gain and minimum start force fixed it for one builder.
FAQ
How much does it cost to build the SO-101 (SO-ARM101)?
About $230 to $330 in parts at current prices, Leader plus follower pair. Low end is the official BOM total ($229.88) using Alibaba servos; high end uses US retail servos at about $20 each. Excludes 3D printing (or about $30 for printed parts from Seeed), a computer, cameras and shipping..
Do I need a 3D printer for the SO-101 (SO-ARM101)?
Yes. PLA+, 0.4 mm nozzle at 0.2 mm layers, 15% infill, supports on. Print the gauge files first to check servo fit. Single-plate files exist for Ender (220 mm) and Prusa (205x250 mm) beds.
Is there a kit for the SO-101 (SO-ARM101)?
Yes: Seeed Studio, Seeed Studio, Alibaba (official BOM footnote), WowRobo, PartaBot. Check what each kit leaves out before ordering.
Buying guides for this build
- Best 6 axis robot arm kit to build yourself
- Best beginner robot to build
- Best servo for a DIY robot arm
- Cheapest robot arm to build
- STS3215 vs Dynamixel XL330
- Which STS3215 gear ratio do I need?
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Last checked 2026-10-25. Sources: github.com · huggingface.co · github.com · github.com · github.com · www.seeedstudio.com · www.seeedstudio.com · www.seeedstudio.com · www.seeedstudio.com · www.waveshare.com · akizukidenshi.com · akizukidenshi.com · akizukidenshi.com · openelab.io · openelab.io · openelab.io · www.robotshop.com · www.adafruit.com