I bought this to replace a broken one, thinking it was middle of the road on price.
However, the diameter of this piston including the rail fins is 21mm.
The width piston for most V2. gearbox including my broken one is 22mm width.
Subsequently this Military Action piston width is 1mm too short and does not stay on the mech box rails, it derails and causes the sector gear to rise and thus lock against the mech box and subsequently lock the spur gear.
Therefore I would recommend you measure the diameter of you existing piston before purchasing this one.