The ultimate self drilling woodworking screws with almost 35 years of unsurpassed performance and long term reliability. Built and tested to outperform any other exterior type screw in any material type in the harshest of outdoor environments. Fastap DuracoatXT exterior screws have tested at 3 times greater in corrosion protection than any other exterior screw in the market. ASTM salt spray tested at 3,636 hours with no red rust after being.. See full description for further details