AFCO Cast Iron Brake Hub & Rotor Flat 1979 And Up GM Style 1.00 Inches Thick 10 1/2 Inch Diameter 5 Inch X 5 Inch Bolt Pattern - 5/8 Coarse Studs - 9850-6500The GM metric rotor is designed replace any stock GM metric rotor. Each rotor has been manufactured using premium grade alloys for superb thermal shock stability, double disked ground to ensure precise flatness, uses high strength 5 8" wheel studs installed on a 5 on 5" bolt pattern, and has been machined for 4 3 4" pattern as well. For the best stopping power, use AFCO brake pads with this rotor. You will not believe what you have been missing out