Because of the narrow tolerances required for the thickness of the rolled material, SKF backing bearings are produced with a running accuracy to P4 specifications, or better. In addition, the tolerances for the cross sectional height of the bearings are very tight, see table.
Depending on the tolerance range, the backing bearings are normally graded in three groups where the height difference is 5 μm. The position of maximum wall thickness is marked by an arrow on the side faces of the inner and outer rings. The consecutive number of the bearing is marked to the left of this arrow and the cross sectional height group is marked to the right.