Sendzimir bearings are mostly used on multi-roll cold mill with thick wall of outer ring. They have the advantages of simple geometric shape, high manufacturing precision and high radial bearing capacity. Because radial load born by Sendzimir bearings is very big, outer ring of bearing must have enough strength, to avoid fracture and deformation of race caused by rolling force.Wall of outer ring for Sendzimir bearings is very thick, main tolerance precision requires wall thickness difference. Group according to wall thickness difference of bearing when used in group. Sendzimir bearings produced by WZZZ can be grouped in P5 grade, P4 grade and P2 grade according to standard of ISO492. Grouping tolerance for each group of wall thickness difference can be regulated in production protocol of user.