Standard Picatinny-style M1913 rails adaptable to most rifles and shotguns. Offered in different lengths with mounting hardware. Will fit vent hole spacing on AR-15 handguards. Heat shields do not have to be altered. Since this is a universal kit, some modifications to the firearm or other hardware may be needed for installation. Rail comes with mounting hardware. Base is 0.588" wide where it mounts to the firearm and 0.835" wide across the rail itself.