This single chamfer wheel nut (561254) replaced the double chamfer 1" long nut (217361) in an attempt to reduce the likelihood of the wheel stud unscrewing with the nut. Didn't work, so a knock in serrated wheel stud was introduced for a short period, but the small nut diameter (59/64" AF) continued to damage rims, this size was increased to 1 1/16" AF to spread the loading (576103). Soon after larger wheel studs were introduced (M16) but nut size remained 1 1/16" (27mm) AF but with an M16 thread (RRD500010)