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Mongoose Legion Complete BMX

What the checker saysnot checked

No fit check runs on a complete bike, and we will not pretend one does. A complete bike does not fill a slot in the builder, so the checker has no counterpart to compare it against and has never produced a single sentence about one.

Open it in the builder

The checker compares the dimensions listed in what we check, and what we don’t. “No conflicts found” means no conflict among those dimensions — not a guarantee that a build works. Errors mean it won’t fit; warnings mean it works but check; infos are notes.

$299.99 to $429.99 MSRP

What the maker states

Wheel size
Built for a 20" wheel
Rear axle
14mm (on 2 of 3 variants)
Head tube
Integrated-1-1/8 (on 2 of 3 variants); Threaded (on 1 of 3 variants)
Crank pieces
3-piece cranks (on 2 of 3 variants); 1-piece cranks (on 1 of 3 variants)
Bottom bracket shell
Bottom-bracket shell american (on 1 of 3 variants); Bottom-bracket shell mid (on 1 of 3 variants)
Rear brake mount
U-brake (on 2 of 3 variants)

A value shown as a set or a range differs between this model’s variants and is never one variant’s spec.

3 verified variants

VariantRear axleHead tubeCrank piecesPrice (MSRP)WeightSourceLast checkedBuild
Legion L20 - 20in14mmintegrated-1-1/83-piece cranks$299.99not statedmaker’s page2026-08-10Build with this
Legion L60 - 20in14mmintegrated-1-1/83-piece cranks$429.99not statedmaker’s page2026-08-10Build with this
Legion Mag - 20innot statedthreaded1-piece cranks$319.99not statedmaker’s page2026-08-10Build with this
What the maker states10 stated·5 not published
  • Built for a 20" wheel.
  • Rear axle 14mm (on 2 of 3 variants).
  • Head tube integrated-1-1/8 (on 2 of 3 variants); Head tube threaded (on 1 of 3 variants).
  • 3-piece cranks (on 2 of 3 variants); 1-piece cranks (on 1 of 3 variants).
  • Bottom-bracket shell american (on 1 of 3 variants); Bottom-bracket shell mid (on 1 of 3 variants).
  • Rear brake mount u-brake (on 2 of 3 variants).
  • Driver cassette (on 2 of 3 variants).
  • Driver 9 teeth (on 2 of 3 variants).
  • Sprocket 25 teeth (on 2 of 3 variants).
  • Tire width 2.3 (on 2 of 3 variants).

5 further fields the checker looks for are not published by Mongoose, so we leave them blank rather than estimate them, and those 5 checks stay silent on this complete bmx. They are size class, top tube, seat system, front brake mount and spindle diameter. Each is recorded as “not stated by the maker (not checked)”.

Source: each variant links the maker’s own page in the table above. Last checked 2026-08-10.

Where this sits

Mongoose Legion is the first model on that list.Next: Mongoose RebelAll Mongoose complete bmxsOpen the BMX builder