This Jendyk Mack Pin Thread Chaser is designed for quickly and easily repairing the internal threads in housing bores of 10,500- and 12,000-lb. axles on Mack trucks with your breaker bar or ratchet. This tool is a better alternative than a machine tool tap, which is not commonly found in the truck servicing garage. This tool has leading threads near each end face for reversibility and easy repair of internal threads while saving the spindle assembly. The patented design, heat treating, and plating process extend the longevity of the tools in this kit.