Medium ranges from grade 120 to 180. Flexible foam pad enables user to sand hard-to-reach areas such as headlight openings, around door handles, door jambs, etc. Helps to eliminate finger marks and can be used wet or dry. 3M(TM) Softback Sanding Sponges are coated with aluminum oxide mineral. Each grade uses a range of mineral sizes. Medium ranges from grade 120 to 180.