Diamond drill bits are made of high-quality Metal material, with nickel-plated , high strength and high hardness. Most of the materials on the market are diamond and white corundum, our hole saw drill bit kits is made only of Metal, which has longer-lasting durability and stability. The hole saw drill bits are designed with enlarged drainage holes. Please add water to cool down during use. The side slots can help cooling water enter and discharge debris from the drilled holes. The tail of the glass drill bit is reinforced and welded, and the drilled holes are flat and smooth without damaged edges, providing high-precision, and smooth drilling experience, improving drilling efficiency. 12 different sizes: 3mm(0.12inch), 6mm(1/4inch), 8mm(5/16inch), 10mm(3/8inch), 12mm(1/2inch), 14mm(0.55inch), 16mm(5/8inch), 18mm(11/16inch), 20mm(3/4inch), 22mm(7/8inch), 26mm(1.02inch), 30mm(1-1/5inch), to meet different drilling needs. Suitable for glass, tiles, ceramics, marble, , fiberglass tiles, , and other materials. Compatible with most electric drills. Colour:As Shown Material:Metal Package Contents: 12 x Diamond Hole Saw Bits (1 each for 3/6/8/10/12/14/16/18/20/22/26/30) 1 x Slotted Screwdriver Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.