Self Drilling Screw - Hex - With Dome Washer (a.k.a Polycarbonate Washer)Self-Drilling Polycarbonate Roofing Screw provides single step installation with no pre-drilling required. The unique cutting head ensures the correct size expansion hole is pre-drilled and the screw is centred. The Hex Head for a quick and secure fasten into steel and a Dome Washer ensures the hole has a water tight seal. Similar to a sheet metal screw, multi-purpose self-drilling screws have a drill-shaped point to cut through the substrate thus eliminating the need to drill a pilot hole. Designed for fixing into metal applications such as fixing fibreglass roof sheeting profiles on to steel purlins, where a  Double Grip action is required. Fixing Polycarbonate roof sheeting to metal battens Description: These Wingfix roofing screws have a hex head with a dome washer and a drill point. They are available in four sizes.Features:Self drilling roofing screw with no pilot hole requiredChoose from sizes 12g x 85mm and 14g x 50mm, 14g x 65mm & 14g x 85mm to suit your jobMade from class 4 galvanised steel or B8 coated steel for resistance to corrosion in outdoor environmentsPolycarbonate Roofing Assemblies 12 gauge-14 threads per inch x 35mm long screw class 4 coatingPolycarbonate Assembly screws are for fastening the crest of polycarbonate profiles to steel.The Class 4 corrosion protection system meets the requirements of ISO 9223 Category 4 (Outdoor application for moderate and severe environments).AS 3566.2 (Self drilling screws for the building & construction industries) specifies the corrosion protection systems required on screw fasteners Classes 1, 2, 3 & 4 where Class 1 is intended for indoor application and Class 4 for environments up to and including ISO 9223 Category 4 (Severe industrial and severe marine environments).