SO-ARM100 vs SO-ARM101: What's Actually Different?
LeRobot Guide
The SO-ARM101 is not a reskin of the SO-ARM100. Its leader arm was redesigned — mixed gear-ratio servos and new joint-3 wiring — while the follower arm is largely carried over, and both arms still run on the same LeRobot software. If you already own SO-100 parts, read the compatibility section before assuming any of them transfer to a 101 leader build.
Researched from Seeed's own SO-ARM10x specifications · No compatibility claims we can't back up
What changed in the SO-101 leader?
The SO-100 leader uses uniform 1:345 gear-ratio STS3215 motors throughout. The SO-101 leader mixes them: one 1:345, two 1:191, and three 1:145 — different torque and speed trade-offs per joint. Assembly also got simpler: the SO-101 removes the gear-removal step the SO-100 build required.
What changed in the wiring?
Joint 3 on the SO-100 leader was a known awkward point in the build. The SO-101 redesigns the joint-3 wiring as part of the leader rework — one more reason leader parts are not a carry-over item between the two generations.
What stayed the same?
The follower, mostly
Seeed's own combined SO-ARM10x specification lists the SO-101 follower motors as “Same as SO-ARM100.” That strongly suggests the follower design carried over — but it is a motor-spec statement, not a part-by-part printed-part guarantee (see the honesty box below).
The software
Both generations live in the same LeRobot repository and workflow — teleoperation, data collection, and training carry across.
The printed-parts problem
Neither generation's official kit includes the printed frame. Seeed sells the SO-ARM101 skeleton separately (leader 12 pieces / follower 11 pieces), and printed parts remain a separate line item either way.
What does each route cost?
Seeed SO-ARM101 kit
$220–$240
Standard / Pro. Printed parts run about +$35 on top, are frequently out of stock, and the kit ships from China.
AI-DEN SO-ARM100 printed parts
$39.99
Compare at $59.99. Leader 13 printed pieces + follower 12. Printed parts only — no motors or electronics. In stock, ships from the US.
Will AI-DEN's SO-100 printed parts fit the SO-ARM101?
For the leader: no — do not buy them for that. The 101 leader is a different design (different gear ratios, different joint-3 wiring), and Seeed sells its frame as a separate product.
For the follower: probably, but not proven. The motor specs say the follower carried over; nobody has published a part-by-part fit guarantee, and we won't claim one until we've test-fit physical parts ourselves.
Building a 101? Email service@ai-den.co and we'll give you a straight answer for your build rather than a guess.
Which arm should you build?
You already have an SO-100 servo kit
Build the 100. It's the proven path, the LeRobot docs are mature, and printed parts are on the shelf in the US — our SO-ARM100 bundle is $39.99, printed parts only, in stock.
You're buying new
The 101's leader redesign is real progress. Buy the 101 kit knowing that — and budget the printed parts separately, whoever you get them from.
You have no printer either way
That's the step we remove for the SO-100 today. For a 101 build, ask us before ordering anything.
Questions, answered
Is the SO-ARM101 just the SO-ARM100 with new colors?
No — the leader's motors, gear ratios, and joint-3 wiring all changed. The follower and the software are the carry-overs.
Can I use SO-100 leader parts on a 101 leader?
No. Different design; treat them as separate part sets.
Can I use SO-100 follower parts on a 101 follower?
Likely, based on the shared motor spec — but unproven part-by-part. We don't sell them as 101 parts until a physical test fit proves it.
What does AI-DEN actually sell?
Printed frame parts only — for the Koch arm ($24.99, leader + follower) and the SO-ARM100 ($39.99). Motors, electronics, wires, and fixtures come from your servo kit.
How fast is shipping?
Orders process in 1–3 business days; standard US delivery is 5–10 business days after processing. 30-day returns on unused items in original packaging.
Building the SO-ARM100?
Shop the SO-ARM100 bundle — $39.99 Start LeRobot without a printer
Building a 101 instead? → service@ai-den.co