?Latest generation ceramic alumina grain with a unique grinding aid that provides 2X-5X performance over zirconia alumina on stainless, alloys and other hard-to-grind materials?Type 27 have a flatter angle and are best used on flat surfaces for blending and smooth finishing?Plastic backing plates add some conformability and are trimmable?Medium/80 grit for light blending and cleaning?Y-wt. polyester flaps for significantly improve life, grain retention and fray resistance?Flap discs are versatile grinding and finishing tools having four main components: abrasive flaps, flap density (how the flaps are stacked), backing plate (flat or conical shape), backing plate material (fiberglass/resin, plastic, aluminum). All flap discs have flaps that are overlapped and glued to the backing plate. The flaps wear during use exposing new abrasive grain. The different variations of the components above provide a variety of choices ranging from heavy stock removal to blending to finishing. Flap discs are designed for portable grinder applications and can be the preferred choice over depressed center wheels or fiber disc.