BLACKHAWK!"s Medium Locking Rail Panel protects unused rail areas from damage while providing a gripping surface that shields the operator from weapon heat and sharp rail edges. Made of a tough, ridged polymer and utilizing the patented Rail-Lock integral locking mechanism to keep them securely in place, these low-profile rail panels improve feel and weapon control. Medium version is perfect for 1/2 coverage on an AR-15/M4 Carbine length fore-end rail.