M-6375-R00 (8-bolt) = made of aluminum 164- tooth ring gear. Fits Cobra 4.6L/5.4L DOHC 4-valve engines & other Mustangs w/8-bolt. Reduced rotating mass for faster engine acceleration in race applications. Fits 105" & 11" clutch. Meets SFI 1.1. 4.6L engines may have 6 or 8 bolts to attach to the crankshaft. Check the engine code before ordering. Romeo-built engines have 6 bolts and Windsor-built engines have 8 bolts. All Cobra engines have 8 bolts. The 8th character in the VIN is (X) for Windsor engine plant or (W) for Romeo engine plant. NOTE: photos & specs can vary