A complete upgrade kit for the ASW338LM airsoft sniper rifle (Ref. 17138), it consist of the zero trigger assembly (Ref.17219) and the M150 cylinder set (Ref. 17249) with a stainless steel cylinder, brass cylinder head, piston, M150 spring and spring-guide, all assembled, ready as a drop-in installation and . With this upgrade the ASW338LM will have a muzzle velocity around 150 m/s or 492 fps.