Norton 9-Inch Back-Up Pad For A290 Hook-and-Loop Discs and Porter Cable Drywall Sander 7800 (Pack of 1) Back-up pad provides extra support to a right angle grinder, enabling the use of heavier pressure when sanding Works with 9" diameter Norton A290 hook-and-loop discs for Porter Cable drywall sander, model 7800 (sold separately) Hook-and-loop abrasive discs can be removed and reattached multiple times with no loss of adhesion, which can increase abrasive disc life Provides flex to prevent tearing or ripping of sand paper Hook and loop design 9-Inch Back-up pad