9407 spring hinge. Manufactured with cold-rolled steel, Closing speed is adjustable, Fits standard hinge cutout and holes, Tension is adjustable, 5/8 inch radius round corners, and Hinge is UL approved for fire doors which must use a minimum of 2 spring and one conventional hinge per. Doors weighing up to 50 pounds require 1 spring hinge, doors up to 85 pounds require 2 hinges, and doors up to 110 pounds require 3 hinges. Additional hinges must also be 4 inch. Designed for doors measuring up to 3 feet wide by 7 feet tall.