1. 1/2"-13 X 5-1/2" UNC Flat Head, Socket Drive, Cap Screw. 2. Titanium flat head screws are much lighter than the alloy ones. 1) Material: Gr. 1, 2, 5, 7 and 12 Titanium.2) Specification: Metric, DIN, UNC and UNF. 1/2"-13 X 5 Titanium Flat Head Screw