Hex washer head self drilling screws have a hex head designed to be driven by a wrench or socket.These screws tap their own holes using their self drilling point to pierce through 20 to 14 gauge metals.Their threads also cut into the material for better retention, particularly in wood. The higher the number the larger the drill point to pierce heavier gauge metals.The heads use a hex nut driver 1/4, 5/16 or 3/8 depending on the size of the screw.These screws are used in the exterior elements.These screws come with features which help them in tackling the constraints of metal to metal fastening.The screws are heat treated to increase their strength and holding abilities exponentially.It is available in carbon steel to bear more wear and tear while also making it more corrosion resistant.