These premium grade cast iron hats make it possible to use bolt-on rotors on vehicles equipped with OEM internal shoe parking brake assemblies. Each hat is a precision machined, threaded hole design for use in conjunction with through-hole mount rotors. After machining, the hats are electro-coated for corrosion resistance. Used for big rotor brake kits on truck, SUV, and 4WD axles with either 6 or 8 lug configurations.