416UNP Finish: Unplated Soss now offers a complete line of Fire Rated invisible hinges. Whatever the door or opening, there is a SOSS hinge for you. Whether your doorway is made of wood or metal, rated 20 minutes or 3 hours, there now is a Soss fire rated hinge that will comply and still give you the "uniquely invisible" hinge that you expect from Soss Features: -Material: Alloy / Stainless Steel. -Matl. Thickness of 1-3/8", 90/180 min UL Fire Rating, 1 each.