DURABLE: Our 10 pack 40 grit flap disc 4-1 2 inch abrasive wheels are constructed of industrial grade premium blue zirconia for strength, durability, and extended disc life. | HIGH DENSITY: Our industrial grade zirconia flap sanding discs are made with a fiberglass backing that effectively absorbs vibrations without smearing during usage, bringing a more stable and efficient grinding. | HEAVY DUTY SANDING DISCS: This 40-grit bevel angle grinder sanding disc is built for grinding, blending, and finishing on a wide range of metal for grinding, blending, and finishing on a wide range of metal | APPLICATION: Bevel Type 27-disc build is effective for blending, smoothing, finishing flat surfaces, deburring, and grinding contours. Perfect for radius grinding on steel, sheet metal, welding, machining, heavy duty equipment and industrial maintenance. | QUALITY: These 4 1/2 grinding wheels are constructed with a fiberglass backing plate to help absorb vibrations and reduce smear during use. Our flap disc set makes it ideal for high performance blending and stock removal on metals and other uneven surfaces.