Description: Titanium coated to reduce friction and heat; High-speed steel step drill, nice quality and durable; These drill bits works great in making a smooth, clean and perfectly round hole; Suitable for punch holes through sheet metal, steel plate, aluminum plate, brass or wood; This drill bit set includes 3 sizes (4-32mm, 4-20mm, 4-12mm), which meet your different needs perfectly; Specification: Material: High-speed steel 4241 Surface Treatment: Titanium Coated Dimension ( L x W x H ):110 x 85 x 35mm/ 4.33 x 3.34 x 1.37'' Size for Each Piece: 4-32mm: 4,6,8,10,12,14,16,18,20,22,24,26,28,30,32mm 4-20mm: 4,6,8,10,12,14,16,18,20mm 4-12mm: 4,6,8,10,12mm Package Includes: 3 Pieces HSS Spiral Drill Bit Set