for cutters from subgroup FT917 equipped with an upper bearing
ball bearing D=12/d=8/h=3, 5 dedicated to cutter index FT917-1208-0001
ball bearing D=16/d=8/h=5 for cutter index FT917-1608-0001
ball bearing D=19/d=8/h=6 for cutter index FT917-1908-0001
ball bearing D=21/d=12/h=5 for cutter index FT917-2112-0001
made of quality steel dedicated to ball bearings