[COATED SCREWS] 2.5 mil of computer controlled powder coating apllied over zinc plating and chromate sealer. Resists harmful UV rays and chemical breakdown. Completely free of volatile organic compounds (VOC), and is entirely recyclable [ZXL NO RUST] 5/16" Cupped HWH is manufactured from a strong ZAMAC zinc-aluminum alloy. Molded Head encapsulates the EPDM washer, which fits neatly and conforms to the inside of the mold [KS LO-ROOT THREAD DESIGN] Fastener thread transitions from fine to coase. The low root design provides excellent pullout strength versus traditional or HI-LO thread forms [MICRO-BIT POINT DESIGN] Drill point design consistently penetrades metal panels, eliminates the need to "punch" the metal panels with a sharp point to start the drilling process. MB point is excellent for penetrating multiple thicknesses of steel often found on ridge cap or trim applications We carry a wide variety of product ranging from bolts, nuts and washers to threaded rod, pipe flashings and connectors. Visit our Amazon storefront to view all items. ZXL Woodbinder screws are self-drilling screws designed to attach metal roofing & siding to wood purlins on post-frame & residential metal roof applications. Stitch screws are designed specifically to fasten overlapping panel together. 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. 5/16" cupped HWH with a molded ZAMAC 5 Zinc-Aluminum alloy provides lifetime protection against red rust on the head & washer. The ZAMAC 5 alloy provides more strength than more common ZAMAC 3 alloy. You may obtain a free copy of the written warranty upon request. Washer face design helps to capture rubber EPDM washer even when driven at an angle. Threads transition from fine to coarse to generate superior holding strength in various wood substrates. Sharp point with pronounced lead thread consistently drills high-tensile 29 & 26 gauge steel with no “point walking".