Precise Drill Point cutting edges and fine thread or a coarse thread to drill with less effort is the main feature of a self-drilling screw. These are used for fastening two different types of materials together. Hexagon Self-Drilling Screws are widely used in metal working. SIZE 5.5mm – 6.3mm in different lengths MATERIAL: Stainless Steel (GI), Carbon Steel DIFFERENT SUITABLE COLOR CAPS ARE ALSO OFFERED