H212 Adapter sleeve with Φ55mm bore diameter. Adapter sleeves are the most commonly used components for mounting bearings with a tapered bore into a cylindrical shaft seating. They are easily to mount, and require no additional location on the shafts. Adapter sleeves consist of three elements: the actual sleeve, a toothed washer MB (for large sleeves lock washer of MS-type) and a lock nut KM or HM-type. The adapter number denotes the complete assembly of adapter sleeve, locknut and lockwasher.As the name implies, adapter sleeves adapt themselves to the shaft diameter, so that higher diameter tolerances can be permitted than those for the seat of a bearing with a cylindrical bore. However, the form tolerances must be kept within narrow limits as the accuracy of form directly affects the running accuracy of the bearing.