8MM ENHANCED BALL BEARING GEAR BOX FOR M4 || SPECIFICATIONS || MATERIAL: METAL, POLYCARBONATE GEARBOX TYPE: VER.2 COMPATIBILITY: M4 / M16 SERIES AIRSOFT AEG RIFLES FEATURES: - REINFORCED METAL ALLOY CONSTRUCTION - 8MM BALL BEARINGS INCLUDED - M4 / M16 SELECTOR & TAPPET PLATES INCLUDED - COMPATIBLE WITH STANDARD VER.2 GEARBOX UPGRADE PARTS