What You Will Get?10 Pcs 6mm -- 30mm6mm / 12:23 "8mm / 0.31"10mm / 0.39 "to 12mm / 0:47"14mm / 0:55 "16mm / 0.62" 18mm / 0.7 "20mm / 0.78"22mm / 0.86 "30mm / 1.17"Features:1. Easy to use, Can be used with a standard electric drill (not included)2. High-quality,nickel-plated with a diamond dust coating.3. Good performance, excellent for making the clean and accurate holes.4. Wide range of uses, can remove a complete circle from glass, ceramics, porcelain, porcelain flakes, limestone, slate, marble, granite, pumice, and fiberglass, or other materials.How to use it?Step 1: Clean the surface and mark the location of the lower hole, angle drill 45 degrees, and slowly start drilling.Step 2: Use water to keep it wet.Step 3: The hole is being drilled at a low speed. Once the hole appears, turn the drill bit to a vertical position.Step 4: Slow down and drill the hole off, for out of the hole to prevent a breakthrough.Note: If you smell burning, back off! Either your speed is too high, or you are applying too much pressure. Your drill should not be hot, or even warm.The general rule is that the smaller the diameter of your drill bit, the faster you can use your drilling speed. The harder your material is, the slower the drill speed you should use