This authentic OEM sourced replacement part is specially designed for use with Dynabrade power tools. Bearings are used to reduce friction between rotating parts, the rollers take the load and spin, distributing the weight evenly while the minimal contact area reduces friction. Make sure to check appropriate diagrams of your model for the...Read more correct location and application of this part. Over time components tend to wear out and may begin to fail eventually requiring a replacement. Keep in mind this high-quality steel bearing is sold individually.