Take your pick or just take both to fit your needs for a carbine length X2 for outdoor games or the compact X1 one for CQB, Evike.com give their take on the APS G-BOX CO2 Blowback Series. The APS G-BOX gas blowback gearbox system is a high-quality, full-metal construction that is compatible with AEG components such as the receiver, handguard, stock, pistol grip, fire selector, magazine release, and charging handle.