I have a g&g arp9 with an ssg gearbox inside. Externally, i just took if the muzzle device and put on a buffer tube with magpul stock. Internally, i put in the following: -Gate Titan Basic -SHS 13:1 Gears -SHS 15 Tooth Piston -Prometheus Blue Bucking -Prometheus Shims -Prometheus M120 Spring All of the internals are new and barely used, but the gun is having issues with firing. Meet up at tac or gateway in socal. Cash only, no shipping.