Truss wafer head self tapping screws are designed for thin steel to wood, wafer head self drilling screws are designed for steel-to-steel attachments. The flat profile head makes these screws great for everything work to attaching closer. Wafer screw of we provided can be locked, no worry after the screw be attach the head still can move. surface include Black Phosphate / Gavanize / Grey phosphate/ colorful. Ect.