Sealtite ZXL Tapping Steelbinder screws are designed to attach metal roofing & siding to metal purlins on commmercial & residential metal roof applications. These tapping screws work well as rescue screws, as they're great for replacing loosened screws in older structures. 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 ZAMAC 5 Zinc-Aluminum Alloy provides lifetime protection against red rust on the head. The ZAMAC 5 alloy provides more strength than the more common ZAMAC 3. You may obtain a free copy of the written warranty from Sealtite upon request. Washer face design helps to capture rubber EPDM washer even when driven at an angle. The type AB point requires pre-drilling for the installation of this fastener.