FLAP DISC 115 x 22.2mm A flap disc is an abrasive product found in the coated abrasive family. The discs are made up of many layered, overlapping sections of abrasive material or �flaps� (hence the name). These flaps are formed of a polycotton or polyester backing material to which abrasive grains are adhered, these are then layered and bonded to a backing plate. The backing plate provides stability to the flap disc and imparts its own unique properties to the product.