These Forgefix TechFast Hex Head Roofing Screws are designed for fixing cladding and sheet steel to light section steel purlins between 1.2mm and 3.6mm. The screws feature an 8mm hex head and are self-drilling. They include a rubber washer that expands under pressure to form a permanent weather seal. For superior corrosion resistance, they are zinc plated and have an Elementech coating, salt spray tested to 1000 hours. This variant features a size of 5.5 x 57mm and comes in a pack quantity of 50.