Ninjago

Arin's Spinjitzu Battle Mech

A small mech that actually spins, and that changes everything about how it plays.

Brick Rated Score

3.9/5

Set 71839 · 2025

Pieces213

Minifigsn/a

Year2025

Set number71839

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The verdict

I clicked the ripcord on this thing three times in a row before I even finished reading the instructions, and that tells you everything about why this set works.

It is a small, honest Ninjago mech built around one good trick rather than ten mediocre ones, and Arin as a torso-up minifig pilot is a fun, slightly goofy touch that kids get immediately. I would not buy this for a display shelf or for someone chasing part count value, but as a toy that gets picked up and played with over and over, it earns its spot. If your kid is deep into the Dragons Rising era of Ninjago, this is a genuinely satisfying pocket-sized build.

Best for: Kids and Ninjago fans who want a mech built to be played with, not shelved

The full review

What it is

I will admit I went in expecting another forgettable small mech, the kind that gets built once and then sits in a bin. This one surprised me. The moment I found the ripcord and gave it a proper yank, the whole upper body whipped around in a full Spinjitzu spin, and I actually laughed out loud. It is such a simple mechanical idea, a cord wound around an axle, but LEGO's designers clearly understood that the fun of Ninjago has always been about spinning things, and they built the entire set around delivering that one moment well.

The catch

I do want to be honest about where this set falls short. At 213 pieces it is a modest build, and if you are the kind of collector who weighs a set by parts per dollar, this one will not win you over. The mech itself is fairly simple once you strip away the gimmick, blocky legs, a boxy torso, and Arin's minifig top half slotted in as the cockpit rather than a full seated figure. There is also not a lot else in the box beyond the mech and a small companion piece, so once the novelty of the spin wears thin for an older kid, there is not a ton left to keep them building or rebuilding.

Who it's for

This is a set for a specific person, and I think it knows exactly who that is. If you have got a Ninjago-loving kid who wants something they can actually grab and play with immediately, one where the whole point is a satisfying physical action rather than careful detailing, this earns its keep. If you are an adult collector building for the shelf, or you want maximum piece count for your money, I would point you toward one of the bigger Ninjago mech sets instead.

The parts story

What the build is actually like, and the pieces worth knowing about.

Building this one is quick and mechanically interesting rather than fiddly. Most of the piece count goes into the legs and the internal spin mechanism, so you spend real time understanding how the ripcord winds around the central axle before you ever see the outside shell come together. It is a good, hands-on build for a younger builder because every step has a visible purpose, nothing here is filler just to pad the box.

The standout piece is honestly the mech's cockpit design itself, the way Arin's minifig torso locks into the chest of the mech so his head and arms become the pilot's controls is a neat bit of clever part use rather than a new mold. Beyond that this is a fairly standard parts palette for modern Ninjago, functional Technic-style pins and axles for the spin mechanism, and Arin's own minifig printing carries the personality since the rest of the build is intentionally simple. At this size and price, the value is in the play mechanism, not in rare or printed elements.

Fun facts

01Arin is one of the newer core ninja introduced in the Ninjago: Dragons Rising era, a former Vengestone miner who becomes Cole's apprentice.
02The set's ripcord spin function is a direct nod to the original Spinjitzu spinner toys that launched the entire Ninjago line back in 2011.
03Small pull-function mechs like this one are designed specifically as an entry point for younger Ninjago fans who are not yet ready for the larger, more complex mech sets in the same wave.