3/4" hex bore. For driveline shafts and transmission on Massey Ferguson 8000, 9000, PA, VE series; White 5100, 5700, 6000, 8000, 9000 (except 6200, 6300 Rear Fold) series planters. For seed and fertilizer transmission on Deutz-Allis 385; Landoll 4400 planters.