Coated with aluminum oxide, 3M™ Softback Sanding Sponges can be used wet or dry when sanding on wood, fibreglass/gel coat, marine paints, metals and plastics. They are flexible and conformable to allow for hand sanding in areas inaccessible to machine sanders. Ultrafine ranges from grade 800 to 1000 grit. The 3M™ Softback Sanding Sponge 02601 has a flexible foam pad enables that enables the user to sand hard to reach areas such as headlight openings, around door handles, door jambs, etc. This sponge helps to eliminate finger marks and can be used wet or dry. These 3M™ Softback Sanding Sponges are coated with aluminum oxide mineral. Each grade uses a range of mineral sizes. Ultrafine ranges from grade 800 to 1000.