ARES Bolt Action Upgrade Kit for ARES TX System Sniper Rifles (MS338/MS700) Package include CNC Cylinder, Bearing Spring Guide, Upgrade Spring, Upgrade Piston and Piston Head Taper Cylinder - Tolerance Taper Cylinder Head - More effective air flow High durability Piston CNC Stainless steel shaft with pressure ball bearing spring guide Suitable for ARES TX System (MS338/MS700) Series Airsoft Sniper Rifle Length: 287mm