This is a NEW special nut designed for 1928-48 Fords with worn rear axle threads. Replacement axles are hard to find and very expensive not to mention the extensive labor to replace one. Many times axles have to be replaced due to worn threads on the hub end. This nut is a standard 5/8-18 internal threads but has special tapered outer thread. when the clamping nut is tightened to the main nut it closes the threads allowing it to “grab” onto your worn threads. We recomend use of Loc-Tite on the clamping outer nut. PLEASE NOTE this is not meant for stripped out threads, or threads that are completely stripped off.