Hex head self-drilling screws, for joining roofing sheets to light section steel (Max. 3.0mm) without the need to pre-drill a hole. Fire Classification: A1" Thread Dia. mm: 4.2 Length mm: 19 Head Type: Hex Fixed Washer Dia. mm: 8.50 Point Type: Self-Drilling Socket Size mm: 6.35 Finish: Zinc Material: Case & Core Hardened Carbon Steel Effective Thread Length mm: 10 Max Drilling Thickness mm: 3.0Size 8 x 3/4 - 1000 Pieces Timco Metal Construction Light Section Screws - Hex - Self-Drilling - Zinc in Silver