HSS Titanium High Speed Steel Cobalt Step Drill SetHigh quality steel Titanium plating to reduce friction and heat Flute design provides faster, smoother and cleaner cutting Suitable for cutting holes in various materials, including steel, brass, wood, plastic, etc. Center punch accurate locator, non slip and crooked Specification: Material: HSS 4241 6 steps: 3 16" to 1 2", (3 16", 1 4", 5 16", 3 8", 7 16", 1 2") 9 steps: 1 4" to 3 4", (1 4'', 5 16'', 3 8'', 7 16'', 1 2'', 9 16'' , 5 8", 11 16", 3 4")