3 8 x 18 High Speed Long Boy Flat Washers Silicon Bronze fine threads and the self fine threads and the self drilling tip make these screws ideal for penetrating and holding into metal framing studs and other types of metal or aluminum framing Coarse threads run approximately 2 3 up the shank to draw the decking tightly to the substrate Straight shank to 1 2” 1 2” reduced shank for sizes above 1 2” M2 high speed steel Sharp cutting edge to drill in many different materials: Mild Steel Cast Iron Aluminum Wood Extra length flute with continuous cutting edges for drilling deep holes and fast chip removal Reduced shank fits all drill motors with 1 2” chucks Non slip grip prevents the bit from spinning in the chuck 3 8 x 18 High Speed Long Boy