Rear-wired or front-wired, G&G Armament got complete gearboxes for the GR-16 as well as the UMG so you can easily replace the existing one... "Our complete gearbox provides the perfect solution for anyone looking to revive their AEG. Easily drop-in the gearbox into your receiver and avoid the complications of assembling your internals. Compatible with any non-blowback G&G AEG.

Contact your local G&G Dealer for availability and pricing."