Used for attaching metal to heavy section steel (Max. 12mm) without the need to pre-drill a hole. NOTE: Partially threaded. Exterior plating gives a reliable and durable corrosion resistant coating which resists 500 hours salt-spray" Thread Dia. mm: 5.5 Length mm: 81 Head Type: Hex Fixed Washer Dia. mm: 12.00 Point Type: Self-Drilling No.5 Socket Size mm: 8 Finish: Exterior (Silver Organic) Material: Case & Core Hardened Carbon Steel Effective Thread Length mm: 53 P/T Max Drilling Thickness mm: 12.0Size 5.5 x 80 - 100 pcs Timco Metal Heavy Section Screws - Hex - EPDM Washer - Self-Drilling in Silver