Quantity: One set (plus an aluminum box) Specifications: 1/4-1-3/8"*1pc3/16-7/8"*1pc1/4-3/4"+1pc1/8-1/2"*1pc3/ 16-1/2"*1 Scope of application: Suitable for workpieces below 25, such as cast iron, carbon steel, aluminum plates, etc. Special note: Do not use for drilling hard metal. PREMIUM MATERIALS: Professional step drill bits are made of high-quality high-speed steel, which is very durable and lasts longer. It has titanium surfaces to reduce heat and frictional cooling. Single drill bits: The HSS step drill bit kit consists of 5 pieces and is easy to use in openings of multiple sizes. You can enlarge the opening to the desired size without changing the drill bit. Precise positioning: The tapered drill bits are suitable for drilling holes with precise dimensions. On the surface of the drill bit, precise size numbers are fixed to facilitate work and avoid misoperation. Easy to use: The double-edged helical structure prevents the drill from rotating and has high efficiency. Compared with the traditional twist drill, the structure is simpler, but the operation is more convenient. Comes with an aluminum case for easy carrying and maintenance. Versatile applications: The step drill bit set is ideal for drilling holes in many materials, such as thin iron, aluminum, thin metal, wood, plastic, steel, brass, etc. The perfect woodworking kit for all craftsmen and hobbyists. Good quality product