This backing flange is a high quality item that is supplied by original tool manufacturer for use with Ryobi angle grinders. Its purpose is to provide support securing the grinding disk. This disc flange is made from durable steel and it is sold individually, please note the clamp nut is sold separately.
The grinding wheel goes between the clamp nut and the disc flange. This part is an OEM from Ryobi for use in grinders. It is made out of a durable material and is sold individually. You may need a wrench and a screwdriver when replacing this item. Over time this part may wear down or break and will need to be replaced.