Our "Bronze Star" screws are designed for exterior professional operations using hard or soft woods, chipboard or other tough materials. The bronze finish is a SKTII coating that gives this fastener extra corrosion resistance. Compatible with chemically treated materials. Pressure Treated CompatibleBronze Coating rated for excellent corrosion resistance, compatible with chemically treated materialsType 17 Notched Extra Sharp Point starts quickly without walking, reduces need for predrilling, cuts through composite materials on first rotationTiny cuts on threads cut through fibrous materials and greatly reduces the torque needed to drive the screw without affecting holding powerKnurled shoulder reams hole in board being fastened, reducing drag on shank and driving tool High quality heat treated hardened steel. True flat head with 16 cutting nibs self countersinks and prevents spinout