National Hardware N226-399 Spring Door Hinge 4-1/2 Inch Square Corner Prime Coat

4-1/2 Inch spring adjustable self closing door hinge, manufactured with cold rolled steel, closing speed is adjustable, fits standard cutouts, tension is adjustable, square corners. Hinge is UL approved for fire doors which must use a minimum of 2 spring and one conventional hinge per door. Doors weighing up to 50 pounds require 1 spring hinge, doors up to 85 pounds require 2 spring hinges. Doors up to 110 pounds require 3 spring hinges. Conforms to ANSI/BHMA Standard A156.17-2004. *NFPA-80 requires fire labeled doors to have a minimum of 2 spring hinges. NOTE: All hinges must have pivot points aligned for smooth operation. Always use same hinge sizes.