10 sizes (diameters): 6mm (1/4 "), 8mm (5/16"), 10mm (3/8 "), 12mm (1/2"), 15mm (3/5 "), 16mm (5/8"), 18mm (11/16 "), 20mm (3/4"), 22mm (7/8 "), 30mm (1-1/5"). Meet most of your different needs. Stainless steel and AMP; Durable: Made of high-strength carbon steel, with a smooth nickel plated surface, extending its service life. Fast, accurate, and amp; Smooth cutting: coated with high-quality diamond to improve drilling speed and form clear, high-precision, and smooth cutting within seconds, without broken edges. Application: Drilled glass, ceramic tile bottles, block jars, fiberglass ceramic tiles, maple slate, transparent granite. Do not use in concrete or depths exceeding approximately 1/2 ". Attention: Please maintain a speed of 800-1000 per minute and continue to add water to keep the drill bit cool. Dry drilling is strictly prohibited