... screw holes(3)--Dia.of roller ball, mm 2:Outer ring with installation bolt holes, innerring with installation screw holes( ... 4)--Dia.of track center, mm 3:Outer ring with installation screw holes, innerring with installation bolt holes( ... with installation screw holes(7)--Precision grade C:Outer ring with installation screw holes, inner ring with installation bolt holes High precision, ...