PTO clutch piston rings for Ford tractor models: 4000 (1968 to 1975); 4110, 4610 (1981 & up); single speed 5000 & 7000, (1965 to 1975); 2-speed 5000 & 7000, (1965 to 1975); single & 2-speed 5600, 5700, 6600, 6700, 7600, 7700, (1975 to 1981); 5610, 6610, 6710, 7610, 7710, (1981 & up); 8000 & 9000 (1968 to 1978)