MATERIAL: Sanding sponges are made from high quality brown corundum, using high density sponges as the base material. Useful and portable. VARIOUS SPECIFICATIONS INCLUDED: 4 medium fine (320-400 grade) sanding sponges in total. To attend to your needs. WET AND DRY AVAILABLE: The sand block is washable and reusable, can be used both wet and dry. It is convenient to clean, durable and easy to grip, not easy to tear. WIDE USE: Can be used on wood, paint, metal, plastic or drywall. Suitable for all kinds of small jobs, can grind any irregular geometric curved surface, portable and practical. A good tool for polishing or cleaning. SAND BLOCK SIZE: 4 pieces/pack. Each block measures 3.9 x 2.7 x 1 inch / 98 x 68 x 25 mm.