Made of high speed carbon steel with nickel plating which is durable and has a long service life, ensures excellent for making a clean and precise hole.6mm (1/4 "), 8mm (5/16"), 10mm (3/8 "), 12mm (1/2"), 14mm (9/16 "), 16mm (5/8 "), 18mm (11/16"), 20mm (3/4 "), 22mm (7/8"), 25mm (1 "), 26mm (1 / 32"), 28mm (1-3 / 32 "), 30mm (1 / 8"), 40mm (1 / 2 "), 50mm (2")Stable drilling at high speed. Drill safely without damaging the border. Creates a precise, smooth cut without broken edges.Simple to use and convenient to use. Water is needed for lubrication when drilling, make sure the bit is kept cool to prevent damage and extend the life of the bitPerfect for Drill Glass, Tile Bottles, Block Jars, Fiberglass Porcelain Tile Ceramics, Mable Slate, Granite Light Stone. Great for home, hobby, crafts, construction, etc.