This product is sponge sand, without sand dropping. It is suitable for polishing surface and polishing the outer casing of the mobile phone. It can be used repeatedly for a number of ordinary sandpaper. The inside is a sponge structure, especially suitable for grinding arcs, arcs, etc., which can be well attached to the arc surface when grinding. It can effectively avoid the non-circle phenomenon caused by ordinary sandpaper grinding. Features: 1. Can be used repeatedly,equivalent to many ordinary sandpaper, it is practical and durable. 2. Inner sponge structure, suitable for grinding curved surface, spherical surface, plane 3. Dry and wet, easy and convenient. 4. Both pneumatic and electric polishers can be used. 5. This product can be used to polish phone shells and paint surface. Specification: Size: approx. 90 * 90 * 90mm / 3.5 * 3.5 * 3.5in Number of holes: 6 holes Thickness: 5mm Quantity: 4pcs Grit size: 300-400#, 1800-2000# (optional) Package list: 4 * Sandpaper Note: There are some errors in the manual measurement, thank you for understanding