Over time, AEGs can fall victim to wear and tear. The M4-A1 Torque Series Mechbox is an upgrade kit designed to keep your weapon kicking in the battlefield. This is an ideal package for airsoft hobbyists and enthusiasts. Includes an M120 spring, rotary spring guide, tappet plate, modular gear set (21.6), selector plate, polycarb pistol, polycarb piston head with bearing, air nozzle with bearing, steel 8mm bearings, anti-reverse latch, modify 8mm Torus mechbox, aluminum cylinder head, cut off lever, and low resistant M4 wiring harness.