Self drilling screw with hex / flange head and EPDM washers. For fixing sheet to timber. Salt spray tested to 1,000 hours. Use these TechFast roofing screws for fixing cladding and sheet metal to timber frames. The self-drilling screws have a slash point for faster insertion, and an Elementech anti-corrosion coating for durability. The 16mm rubber washer beneath the aluminium flange expands under pressure to form a permanent weather seal. These Forgefix TechFast Hex Head Screws are designed specifically for fixing cladding and sheet metal to timber frame work. They have a Hex slash point head and are self-drilling for speedy insertion. The screws have a rubber washer beneath the aluminium flange which expands under pressure and forms 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 TFHT6325 TechFast Hex Head Screws have the following specifications: Size: 6.3 x 25mm.Box quantity: 100.