Specialty Diamond MB40 40 Grit Hook & Loop Triangular Sand Paper (20/pk). They are perfect to use in smaller hard to get areas where you need to sand old paint or rust on almost any surface. Ideal for corners and edges. You can use it on wood, fiberglass, and metals. They are 3-3/16 of an inch per side. They fit most triangular backer pads that usually come with your multi tool and fasten via hook and loop. Also known as Hook & Loop.