Cluster mill or Backing Bearings are multi-row cylindrical roller bearings and are used for 20-high reductions mills and rolling ferrous and non-ferrous materials. These bearings can have rollers that are cage guided or full complement depending on the loads and speeds of the application. A machined brass cage and sometimes a precision ground internal spacer is provided when the cage guided bearing is specified. The heavy section outer race and relatively smaller section inner race and rollers are closely matched to achieve precise section height specifications. The specifications allow for shaping of the backing assemblies to achieve the desired rolled material characteristics. These bearings are section numbered and serialized per specification for backing assembly building/roll shop tracking. They are available in popular backing bearing O.D. and sections heights that match mill size specifications.