Allstar 10-Bolt Differential with 8. 2 inch Ring Gear Mini Spool for GM fits a GM 10-bolt differential with a 8. 2 inch ring gear and 28 spline axles. The mini spool is precisely machined for a proper fit, and then heat treated. The cross pin (Allstar part 68163) must be ordered separately. The unit fits a 1964-72 GM 10-bolt differential with an 8. 2 inch diameter ring gear using 28-spline axles and a non-positive traction case. It is backed by a 90-day limited factory and sold individually.