King Arms Complete Reinforced V3 Gearbox w/ 9mm Bearings for AK Series Airsoft AEG Rifles (Model: M135 / 400-500 FPS)

"Ordered this gearbox assembly for my cheap $40 Aftermath "Kraken Kruz" (Beta Spetsnaz) AK. Works really well. I'm still not too fond of the metal piston head considering they do have a bad reputation with high fire rate systems, which is what I have my gearbox for.

Overall: good replacement for a crappy gearbox. The one I had before in the gun was an ALL PLASTIC piece of crap, and now this King Arms beauty saved my gun from being a useless dust collector. M120 spring as promised, I clocked mine in @ 405fps and fps fluctuation of about 1-2fps. Love it, just maybe go with a regular polycarb piston head for it though!!