Description O-ring, axle housing to center housing. Tractors: 4000, 5000, 7000 (1965-1975), 4100, 4600, 5600, 5700, 6600, 6700, 7600, 7700, (1975 to 1981), 4110, 4610, 5610, 6610, 6710, 7610, 7710 (1981 & up). This item is a suitable alternative for the following: 379313S91, 83417133