This gearbox set replaces the upper half of an ICS M4 / M16 series AEG gearbox and is a complete upgrade for your AEGâ€™s compression parts. With its included M120 spring, this upper gearbox set delivers powerful performance right out of the box and allows your ICS AEG to shoot up to 420 FPS (w/ 0.20g BBs). This upper gearbox easily drops into ICS M4 / M16 series AEGs, saving you time and allowing you to adjust muzzle velocity within minutes. In addition, this gearbox set is compatible with most aftermarket M4 airsoft parts, such as pistons, cylinders and springs.
ICS M4 upper gearbox shell
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