Used for attaching metal to heavy section steel (Max. 12mm) without the need to pre-drill a hole. Thread Dia. mm: 5.5 Length mm: 55 Head Type: Hex Fixed Washer Dia. mm: 12.00 Point Type: Self-Drilling No.5 Socket Size mm: 8 Finish: Zinc Material: Case & Core Hardened Carbon Steel Effective Thread Length mm: 33 Max Drilling Thickness mm: 12.0Size 5.5 x 55 - 100 Pieces Timco Metal Construction Heavy Section Screws - Hex - EPDM Washer in Silver