PSA SANDING PAD: Blue pressure sensitive adhesive (PSA) backing design sticks onto flat vinyl surfaces and is most ideal for woodworking projects; sanding pads for orbital sanders and dual action sanders. QUALITY MATERIAL FOR SANDING: Each 5-inch sander disc is made of high-quality polyurethane material that is lightweight and allows a flexible, but firm touch without feeling stiff for maximum control and efficiency for sanding applications.