Spax 4581820701005 lag-Screws The trend setting low profile built-on washer head design offers a contemporary and sleek finished installation. Excellent draw down strength without the need for a separate washer delivers superior clamping ability and a easier installation Check out our Threads!! our patented thread technology allows the screw to be driven faster, is easier to install, and reduces splitting in wood. Let Spax take some of the hassle out of your next project High Corrosive resistant (HCR) coating makes these screws ideal for use in treated lumber and exterior applications Heat treated Grade 5 Durability. Subjecting the screw to heat treating gives greater strength and reduces breakage T-Star plus head provides superior bit engagement. Better bit engagement means quicker installation with less effort