It is a genuine replacement o-ring which is supplied by the original equipment manufacturer for use with Dynabrade power tools. This item is utilized to provide an air-tight seal between connected parts, please make sure to check appropriate diagram of your model for the correct use and location of this component. Over time o-rings tend t...Read moreo deteriorate and crack eventually requiring replacement to maintain peak performance. It is a high-quality part that is made of durable rubber material and it is sold individually.