DBA's 4000 Series XD variant features DBA's non-directional cross drilled and dimpled rotor design The XD finish provides additional cooling benefits above the HD spec, along with enhanced sports looks, The DBA mix of dimples and drilled holes provides enhanced rotor structural support above transitional cross drilled techniques, DBA recommends a T3 slot for high performance applications, DBA's 4000 Series rotors feature: XG-150 High Carbon Alloyed Iron, TSP (Thermal Stability Profiling), Thermo-graphic paint markings (THGP), Direct replacement suitability, Moisture proof corrosion protection packaging