@High quality diamond drill bits with economical, fast cutting surface? Made of high strength nickel plated carbon steel makes these drill bits durable and precise; the bit tip of the head is made of 80 grit diamond coating, which is uniform; It helps a lot to increase the drilling speed and sharper than other ordinary saws. @10 pcs mainly used sizd? Contains the following diameters: 8mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm, 22mm, 25mm, 50mm; Using laser marking, the size will satisfy most of your different needs. @ application? Suitable for use in a drilled hole on glass, marble, tile, block jars, fiberglass, porcelain and ceramic tile, BLVA0299 slate, light stone granite, etc. It works with all electric drills and impact drills. @Nice design? the center holes and side holes help to easily remove waste material; and nickel plated surface, prolong service life, improve surface corrosion resistance @ notification type? When cutting hard materials, it is important to ensure the cutter is