Retro Arms CZ CNC 8mm Gearbox Shell for SR25 Series Airsoft AEG Rifles

"Works well in my A&K SR25 with a slight modification: the curved part of the back of the lower receiver had to be slightly filed so the gearbox could lower all the way into it. The bushing holes are also extremely tight, to the point that I had to use a (non-marring) pin punch to get them seated properly. The gearbox came with screws and a ball-bearing spring guide.

Additionally, considerations must be made for several components:
- the thickened front of the gearbox requires a longer nozzle, an AUG-length nozzle fit my build perfectly
- the gearbox requires a thinner cylinder; the stock A&K cylinder was too wide

My GATE aster also dropped right in, I just had to dremel away the bump on the other side of the gearbox for the sticker.

Overall 4/5 stars, removing 1 star for being slightly off-spec.