The SSBFHSD screw is a bi-metal screw designed for timber to steel applications (1.2-2.4mm steel thickness). The bi-metal design consists of A4 stainless steel with a carbon steel winged drill point which is perfect for steel joist applications whilst still offering superior corrosion resistance. It has a countersunk ribbed flat head, fine thread and drill point with wings. The wings ream a hole larger in the timber and break off when they hit the steel allowing the timber to be pulled tight to the steel.