Button head socket cap screws are precision threaded fasteners with an internal socket drive (also called allen hex drive) for installing in areas with limited side clearance. The internal hex drive requires an Allen wrench. They are known for their effecient application performance and endurance widely used in a variety of industries such as construction, manufacturing, engineering, assembling, aircraft and so on and serves a wide range of use for professionals, amateurs, landlords, repairmen and DIYers. These screws are available with a variety of head shapes, which determine how the screw interacts with the mating surface, and drive styles, which determine the type of tool required to install the screw. The high quality Class 10.9 Alloy Steel provide perfect strength and good corrosion resistance in bad environments like high temperature, cold weather and high humidity areas without the need for time consuming and costly maintenance. Thread Diameter 6mm Head Diameter 10.5mm Head Height 3.3mm Screw Length 12/16/20/25/30mm (Head NOT Included) Allen Hex Drive 4mm High Quality Class 10.9 Alloy Steel Package Included 150 pcs Button Head Hex Socket Cap Screws Bolts Nuts Washer Assortment Kit Contact Us: If you have any questions when using, please feel free to contact us by Amazon message.