These Forgefix TechFast Hex Head Roofing Screws are designed for fixing cladding and sheet steel to light section steel purlins of between 1.2mm and 3.6mm. The screws have a hex head, are self-drilling and have a rubber washer which expands under pressure to form a permanent weather seal. They are zinc plated and have an \'Elementech\' coating for superior corrosion resistance, which has been salt spray tested to 1,000 hours.The TFHL5538 TechFast Hex Head Roofing Screws have the following specifications: Size: 5.5 x 38mm.Pack quantity: 100.