Self-drilling screws are for use in wood, fiberglass, and metal. They possess a drill point that enables them to drill their own hole in thin gauge steel. No pilot holes are necessary. Screw sizes included: #8 x 1/2", #8 x 3/4", #8 x 1", #8 x 1-1/2", #10 x 1", and #10 x 1-1/2".