1: Suitable for Aluminum, insulation board, PVC board chamfer,steel, aluminum, sheet metal, carbon steel, 304 stainless steel, etc. 2: Made of high speed steel material, far 4241. 3: 118 X Bit Design, you can drill from any angle, no slipping. 4: Triangle , fit for most drill chuck and no slipping. 5: Can drill 5mm thickness material. One drill bit contain lots of sizes diameter. These Double-Fluted Step Drill Bits provide faster cutting and drilling than single flute bits. The easy-to-read step markings and targets save time when drilling holes. Thick 3/8inch hex provides a firm, positive grip and 't spin out in the drill. Two cut faster and keep bit cooler Fast-starting, non-walking drill tip High-visibility silver targets for primary hole sizes Thick 3/8-Inch hex 't round out in the drill chuck for a more positive grip 3 hole sizes(7/8,1-1/8,1-3/8) High-visibility silver targets for primary 19 hole sizes; come with 19 sizes (3/16inch, 9/32inch, 3/8inch, 7/16inch, 17/32inch, 5/8inch, 11/16inch, 25/32inch, 7/8inch, 29/32inch. 31/32inch, 1inch, 1-1/16inch, 1-1/8inch, 1-5/32inch, 1-7/32inch, 1-9/32inch, 1-5/16inch, 1-3/8inch) so you can drill up holes with different diameters, saving your time and efforts to change bits. These Double-Fluted Step Drill Bits provide faster cutting and drilling than single flute bits. The easy-to-read step markings and targets save time when drilling holes. Thick 3/8inch hex provides a firm, positive grip and 't spin out in the drill.. Colour:Photo Color Material:high speed steel Package Contents: 1 x Drill bit Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.