This is a 15 pack of dust caps for the end of rifle muzzles. These caps protect your rifle muzzle from dirt and debris entering and potentially creating a unsafe situation. The caps fit snugly over standard AR-15 and M4 muzzle devices and similarly sized muzzles. The caps are a great way to keep your rifle safe and clean while on the move. If the cap is on your rifle and you shoot, they will just fly off with the first shot so long as they are not overly tight on the muzzle device they cover. If placed on a hot muzzle device there is a possibility of them melting onto the device.