Sanding sponges are used for sanding wood, metal, painted surfaces, and plastic. Sponges are flexible to conform to irregular surfaces and can be used wet or dry. They can be fabric backed with abrasive on one side or can have abrasive material on multiple sides. Choose from very coarse to ultrafine abrasive grade, or corresponding grit, depending on material being worked and level of precision required. Common abrasive materials include silicon carbide and aluminum oxide.