The steel self-drilling screw with zinc plating has a serrated hex washer head and a hex drive. Steel is often used in applications where strength is the primary consideration. The zinc plating offers corrosion resistance and has a reflective appearance. The hex washer head has six flat sides that a wrench can grip to turn from the side, enabling use when there is no space above the head for a screwdriver. The serrated flange acts like a washer to increase the fastener's bearing surface and distribute the clamping force over a larger area, providing a grip that resists loosening.Self-drilling screws, a type of self-tapping screw, are threaded fasteners that drill their own hole and thread it as they are installed. Usually only recommended for use with metal, self-drilling screws are available with wings that enable use when fastening wood to metal. The drill point length should be long enough to penetrate both materials being fastened before the threading portion reaches the material. Steel is often used in applications where strength is the primary consideration Zinc plating resists corrosion and has a reflective appearance Hex washer head has a serrated flange for additional grip on the mating surface that resists loosening Hex drive tightens from the side with a wrench, enabling use when there is no space above for a driver ASIN B00GYLC7OQ Brand Small Parts Color zinc Model 1412KWSMS Head Type Hex Size Name 1/4 -20 Metal Type Alloy Steel Unit Count 25 Count Part Number 1412KWSMS Thread Size 1/4 -20 Thread Type Standard Drive System External Hex Finish Types Zinc Plated Manufacturer Small Parts Thread Style Right Hand Fastener Size No. 3 Fastener Type self-drilling Item Diameter 0.25 inches Material Type Steel Exterior Finish Zinc Item Dimensions 0.75 inches Number Of Items 25 Thread Coverage Partially Threaded Number of Pieces 25 Outside Diameter 0.25 inches Screw Head Style Hex Washer Screw Point Style #3 Set Screw Thread Type UNC Compatible Groove Diameter 0.25 inches