General description These Forgefix TechFast Hex Head Roofing Screws are specifically designed for fixing cladding and sheet steel to heavy section steel purlins ranging from 6.0mm to 12.5mm. The screws feature a hex head, are self-drilling, and include a rubber washer that expands under pressure to create a permanent weather seal. Technical specifications Size: 5.5 x 51mm Pack quantity: 100 Corrosion resistance: Zinc plated with 'Elementech' coating, salt spray tested to 1,000 hours Other information