Quality Materials: 4241 high-speed steel, titanium coating to reduce friction during cutting, easily cut 1-5mm iron, aluminum, wood, plastic, long service life. Proven performance and long life when drilling holes. Multiple Sizes: Step drill bit with five different sizes to meet different drilling size requirements. Automatic Damping: When the level is pressed against the surface of the object, a high impact force is automatically generated, and the adjustable cover can adjust the impact force. The surface is highly non-slip and allows for precise positioning without worrying about errors. Construction FeaturesDouble-groove drill bit and smooth design, prevents cutting drops. Three side handles prevent slippage, and each step on the drill bit is marked with the corresponding size indications. Easy to UseDouble-edged design allows for faster and smoother drilling, so you don't feel stagnation and resistance when using it. It has the best speed and accuracy. When working with the step drill, pour water, can effectively extend the service life. Sizes: No. 1: 6 steps from 3/16" to 1/2" 6 (3/16', 1/4', 5/16", 3/8', 7/16', 1/2') No. 2: 13 steps from 1/8" to 1/2" (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') No. 3: 9 steps from 1/4" to 3/4' 9 (1/4', 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4") No. 4: 10 levels from 1/4" to 1-3/8"' 10 (1/4', 3/8", 1/2", 5/8", 3/4", 7/8", 1", 1-1/8", 1-1/4", 1-3/8") No. 5: 12 levels from 3/16" to 7/8" 12 (1/4', 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4", 13/16", 7/8") Package Contents: 1 x 1/4-1-3/8 Step Drill Bit. 1 x 3/16-7/8 Step Drill Bit. 1 x 1/4-3/4 Step Drill Bit. 1 x 1/8-1/2 Step Drill Bit. 1 x 3/16-1/2 Step Drill Bit. 1 x Automatic Center Punch 1 x Aluminum Box.