Sealtite ST-XL Woodbinder screws are self-drilling screws designed to attach long-life metal roofing & siding on post-frame & residential metal roof applications. Designed as an alternative to the zinc-aluminum alloy head. The smaller cupped HWH provides an attractive low-profile appearance versus larger HWH fasteners. 304 Stainless Steel cap provides lifetime warranty against red rust on the head & washer. Coated screws feature a tough 2.5 mils of powder coating that will not chalk or fade due to the UV inhibitor in all colored coatings. Woodbinder pole barn screws have threads that transition from fine to coarse to generate superior holding strength in various wood substrates. The combination of a sharp point & Type 17 drills 29 & 26 gauge consistently & eliminates the metal shavings that can embed themselves in the EPDM rubber washer.