Description Reviews Fits GM 12P differential 30 spline pinion gear 4.11 ratio Coverage includes ’64 to ’72 Chevelle, ’67 to ’72 Camaro, ’69 to ’72 Firebird, ’70 to ’72 GTO, 9 other models, or anything hot-rodded with a GM 8.875” 12 Bolt Passenger Axle 8.875” ring gear diameter 12 bolt ring gear 2.25" (AK 1563) axle bearings Includes ring and pinion gear set, and all required bearings and installation hardware