Replacement castle nut and cotter pin for King Kutter rotary cutters. This is the nut that mounts the blade pan to the gearbox, fits 4', 5', 6'and 7' cut mowers with 40hp and 60 hp. gearboxes in both 3-point and pull type hitch. This is a flanged type nut that eliminated the washer that was used on early models along with the nut. 1"-14 thread pitch!