General description Specifically designed to attach wood to metal, these TIMCO Self-Drilling Wing-Tip Steel to Timber Heavy Section A2 Stainless Steel Bi-Metal Screws are ideal for applications where maximum efficiency is required. Technical specifications Dimensions: 5.5 x 120 mm Material: A2 Stainless Steel Thread type: Metric thread Maximum thickness of metal: 12 mm Usage Wings designed to ream out the timber, allowing the screw to achieve maximum R.P.M. without burning out. When the wings hit the metal, they break off to permit the thread to self-tap.