Includes 20 replacement sandpapers with hook & loop backing that attach to the flex pad on both the 3" and 4” Sanding Flex accessories, MP21-19-3 and MP21-19-4. You'll have versatility using these replacements on these two units. The sandpaper allows for an overlap of about ½” (12mm) to prevent side accessory marks when used on the 3” Sand Flex pad.