Systema Complete Mecha-Box for M4 / M4-A1/ M4 RIS
- Complete Drop In Gear Box for Retractable Stock Front Battery M4 / M4-A1/ M4 RIS with M120 Upgrade Spring for 370 - 400 FPS
- All internal parts completed upgraded with Systema Parts (gears, bearings, tappet late, cylinder, bearing spring guide rod, selector plate, low resistance wires)
- Includes Torque Up Gear Set with Teflon Cylinder
- Completely Reinforced Heavy Duty Alloy Gear Box
- Not Compatible with ICS or Olympic Arms M4 Series Due to 2 Piece separate Gear Box Design