A joint includes an outer race, a first inner race installed in the outer race and a second inner race installed in the first inner race. The outer race includes an inner surface and first grooves formed on the inner surface. The first inner race includes an outer surface, an inner surface and second grooves formed on the outer surface, and a plurality of third grooves formed on the inner surface. First balls are disposed between the first grooves and the second grooves for transmitting rotation of the first inner race to the outer race. The second inner race includes an outer surface and fourth grooves formed on the outer surface. Second balls disposed between the third grooves and the fourth grooves for transmitting rotation of the second inner race to the first inner race.