It is a genuine manufacturer-sourced replacement part that is supplied for use with Grip-Rite nailers. This is a special o-ring which is utilized to provide an air-tight seal for the driver assembly, for the correct application make sure to check appropriate diagram of your model. Over time o-rings tend to deteriorate and crack eventually...Read more requiring a replacement to maintain the proper seal. It is a high-quality component which is made of durable rubber material and is sold individually.