Description: Size : M2~M8 / 1/16"~5/16" Length : 13~200mm / 1/2~8" Material : Carbon Steel / Stainless Steel Thread Type : UNC, UNF, Type 25 and BSW thread Surface Treatment : Zinc plated, Yellow Zinc plated, Black zinc, Zinc Nickel, Mechnical Galvanized, Ruspert, Slat Spray Test according to customer requirement. Standard : DIN, IFI, JIS, according to customer's drawing Package : Bulk packing, Box packing, Bag packing, Blister Socket head screw Usage: Socket head screw's design has characteristic for W/head screw and W/O head screw, it can increase flexibility in design. About head part can be concave or flat, hex socket hole requires hexagonal wrench or hexagon screwdriver to load. When it is loading, we can hold wrench to adjust distance can save power, therefore, it requires high hardness material to ensure socket head can bear bigger torque to let screw fastened and prevent screw loose from object. It compares with traditional hex bolt, socket head screw is not slide angle easily, and rust on screw to affect disassembly.