SO-101 Joint Spares Kit: 6 Metal Horn Sets + 17 Bus Servo Cables + Spare 25T Output Disc, for SO-ARM100 / SO-ARM101 LeRobot Arms

The SO-101 Joint Spares Kit is the set of parts that wear out or get lost on a LeRobot SO-ARM100 / SO-ARM101 arm — the aluminium servo horns at every joint, the 3-pin bus cables between servos, and a spare 25T output disc — packed as one order instead of four.

Horns strip and cables fail at the joint that flexes hardest, and they always fail mid-build. This kit is every wear part of one SO-101 arm in a single bag: six metal horn sets, seventeen bus servo cables in the lengths the arm actually uses, and a spare 25T output disc — enough to re-horn and rewire a whole arm rather than order one part at a time.

What can you use it for?

• Re-horning a whole arm after plastic or worn horns start slipping on the spline
• Rewiring an arm whose joint cables have failed from repeated flexing
• Building a second arm from servos you already own
• Keeping a complete spares bag in a classroom or lab so a broken arm is a ten-minute fix
• Adding a 40 cm run from the base servo to a controller mounted off the bench

Who is it for?

Anyone running an SO-101 arm long enough to break something — and labs with several arms, where the part you need is always the one you do not have.

Compatibility

• Arms: SO-ARM100, SO-ARM101 (LeRobot SO-101), leader and follower; also LeKiwi and OpenDuck joints
• Servos: Feetech STS3215, STS3250, STS3235, SCS series and other 25T / 5.9 mm outputs
• Cables: 3-pin 5264 (2.5 mm), the connector Feetech bus servos use — not PH2.0 or JST-XH
• Screws: M2 horn screws and M3 centre screws included with every horn set

Specifications

What's in the box

• SO-101 Joint Spares Kit: 6 × STS3215 main + rear metal horn sets with screws, 4 × 15 cm + 4 × 20 cm + 4 × 40 cm 3-pin cables, 5 × 40 cm 3-pin cables, 1 × spare 25T metal output disc

Shipping and returns

Ships from our warehouse in Singapore with tracking. Parts and accessories: free standard shipping on orders over $25 ($4.99 below) to Canada, the UK, EU, Japan, Korea, Australia and most other countries, 5–15 days; to the United States at carrier cost from $27.99 (SingPost) or $109.99 (DHL Express). Assembled robot-arm kits over 2 kg are built and calibrated to order in Singapore (dispatch in 7–10 business days) and ship worldwide at carrier cost: SingPost Speedpost Priority from $124.99 (10–14 business days) or DHL Express from $229.99 (3–5 business days), shown at checkout. 7-day returns; defective items are replaced or refunded with shipping covered. Import duties, where charged by your country, are paid by the recipient.

Frequently asked questions

Does this cover a whole arm?

Yes — one arm. Six joints, six main + rear horn sets, and enough cable to wire the chain with spares. A leader + follower pair needs two kits.

Why does the kit weigh 228 g?

Deliberately. Tracked international shipping is one flat rate up to 250 g, so the kit is built to sit just inside that band rather than tipping into the next one.

Are these genuine Feetech horns?

The horns are 6061-T6 aluminium with the 25T / 5.9 mm Feetech spline and are sold under our own ArmDojo brand, not as OEM Feetech parts. The cables are Feetech-specification 5264 3-pin.

Do I need the rear horn as well as the main horn?

For SO-101 joints, yes. The printed link is clamped between the main horn on the output shaft and the free-turning rear horn on the servo's second shaft; using only the main horn puts all the load on one side.

Can I buy the parts separately instead?

Yes, all three are listed individually. Bought that way they come to $52.96 and ship as separate line items; this kit is $47.99.