Protect the muzzle of your valuable AR-15 or AR-10/SR-25 by performing your cleaning from the breech end. These Bore Guides were specifically designed for the AR-15/ AR10 style semi-auto rifles. Made of Delrin and Aluminum. Includes O-rings and assembly tool. Guides cleaning rod into barrel, O-ring seal prevents oil and debris from coming back into action. Allows brush clearance through inside diameter. Comes with spare O-rings and O-ring assembly tool.