These high speed steel twist drills are great general purpose drill bits, they offer an excellent combination of quality, strength and affordability. Made of the highest quality steel, carefully tempered and accurately ground to size. The drills work for a wide variety of materials including but not limited to silver, gold, low and medium carbon steel, cast iron, wood and plastics. Available in sizes 80 - 50 or 0.0135"/0.343mm - 0.0700"/1.778mm, chart below shows complete size list. Drill length varies depending on the size. These drill have a straight shank, meaning the drill bits have the same diameter throughout the length of the bit, other drills with a standard 3/32" shank are also available along with collet adaptors to use these in 3/32" shank hand pieces. Individual sizes, sold in packages of 10 bits. Always wear safety glasses when drilling.