Richelieu 5823-B 4-1/2 Inch x 4 Inch Spring Square Corner Mortise Door Hinge – Single Hinge Features: Single hinge Features precisely machined square corners Tested for residential and commercial strength application Packaged with 8 wood screws and 8 machine screws for simple, out of the box installation Constructed with 8 screw holes in an arc arrangement for maximum mounting strength Product Technologies: Spring Hinge: These single action hinges are fitted with springs in the barrel to bring an open door back to a closed position automatically. Great where door space is at a premium and door closers are impractical. With double action hinges, the door is able to move in either direction. Material Type: Steel is cheap, strong, and durable, making it a favorite for hinges of all types, despite it being slightly more prone to rusting than solid brass or stainless steel. Mortise Hinges: Mortise door hinges mount flush with the surface of your door, providing maximum strength with the least interference with door functionality. It is recommended that three hinges be used on doors up to and including 7-1/2 feet, with one additional hinge for each additional 2-1/2 feet. Be sure to check your current hinges before making a purchase. Specifications: Height: 4.5″ Width: 4″ Material: Steel Mounting Type: Mortise : 0.125″ Number of Knuckles: 8 Number of Screw Holes: 3 4 1/2 x 4 Brass.