H-302P….Desk Chair Swivel Back Hinge in brass plated steel, but not very brassy. Two of these parts are used between the padded chair back and the vertical upright that holds it. Allows seat back to be tilted up and down at the proper angle for comfort. Unique tight lock friction disc holds back firmly. Two are typically used. Screw mounting plates are 1/2 inch wide by 1-1/4 inch long. Sold by each not pairs.