Ultimate High Performance Gearbox Upgrade Kit for JM Gen. 8

This kit is the Ultimate High Performance Gearbox Upgrade Kit for JM Gen. 8. .Refit requires some hands-on ability   Features: Compatible with JM gen8 models , including: M4A1, SCAR V2, MP5 V2, UMP45 etc Complete upgrade kit Potential performance increase: Rate of fire: up to 20 rounds per second (depending on configuration) Shooting range: 30m FPS 300 Specification: Material: Nylon ABS Metal Package Dimensions: 27*16.5*5cm Package Weight: 390g Package includes: 1 x Singularity Edition Nylon Gearbox Shell 6 x 8mm Bearings 1 x Silver-coated Wire Set (Including Microswitch) 1 x Aluminum Cylinder (Color Random) 1 x Metal Gear Set 1 x Metal 8-hole Piston Head (Color Random) 1 x All Metal Gear Nylon Ladder (Color Random) 1 x 1.2 Wire Diameter Spring 1 x Original Accessory 1 x 1.3 Wire Diameter Spring 1 x 27cm Aluminum Barrel   Please note: The reliability, and performance increase is dependent on the quality of the installation. Professional installation is required.