This is a set of step drills made of high speed steel 4241. Different specifications can meet different drilling requirements. The aluminum box can accommodate and protects the drill bits. Features: Made of fine quality high speed steel, wear resistant, not easy to rust, has a long service life. Double grooves design for faster and smoother cutting. Different specifications can meet different drilling requirements. The aluminum box can accommodate and protects the drill bits. Suitable for workpiece with hardness is less than 25°, such as carbon steel, iron plate, aluminum plate, pvc plate, wood board and so on. Specifications: Material: high speed steel 4241 Quantity: 5pcs Size: 1/4" to 1-3/8" (10 steps): 1/4", 3/8" 1/2", 5/8", 3/4", 7/8", 1", 1-1/8", 1-1/4", 1-3/8" 3/16" to 7/8" (12 steps): 3/16", 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8" 1/4" to 3/4" (9 steps): 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4" 1/8" to 1/2" (13 steps): 1/8", 5/32", 3/16", 7/32", 1/4", 9/32", 5/16", 11/32", 3/8", 13/32", 7/16", 15/32", 1/2" 3/16" to 1/2" (6 steps): 3/16", 1/4", 5/16", 3/8", 7/16", 1/2" Shank diameter: 1/4" to 1-3/8": 8mm / 0.3in 3/16" to 7/8": 8mm / 0.3in 1/4" to 3/4": 8mm / 0.3in 1/8" to 1/2": 6mm / 0.2in 3/16" to 1/2": 6mm / 0.2in Package size: 152 * 107 * 43mm / 6.0 * 4.2 * 1.7in Package weight: 502g / 1.1lb Packing List: 5 * Step Drill 1 * Aluminum Box