Specifications Brand: Golden Eagle Operation: Electric Automatic Material: Metal Gearbox, Lower Receiver / Polymer Motor Grip Muzzle Velocity: 350 Fps (W/.20G Bbs) Gearbox: Version 2 ( Metal) Weight: 2.76 Lbs Color: Black Compatibility: Golden Eagle M4 Full Metal Upper Receivers Package Includes: 1X Lower Receiver, 1X Metal Gearbox Features Type: Full Metal Version 2 (Rear Wired) Shell Construction: Aluminum Shell Color: Black Motor: High Torque Long Type Gears: High Torque Steel Bushings: 7Mm Metal Bearings Spring: M100 Standard Pitch Spring Guide: Bearing Metal & Polymer Cylinder: Metal Ported Cylinder Head: Polymer Piston: Polycarbonate W/ Full Steel Teeth Piston Head: Polymer Ported Air Nozzle: Polymer Tappet Plate: Reinforced Polymer Wiring: Mosfet Silver Wiring (Rear)