Only for cast diesel heads with hardened pre-cups. Fits all overhead surfacers with 1/2 in. diameter tool tip capacity. Will NOT work on standard cast heads. .500 in. diameter. 1/8 in. thick. Won't chip. NOTE: A 1/16 in. thick carbide shim (Order No. CBN-500SHIM) must be used with DRD-500 on al DCM machines.