High Quality Materials: The revolving door hinge is made of high quality 201 stainless steel, which is strong and wear resistant. It opens and closes very smoothly and can be used for a long time. Invisible Design: The door hinge is invisible, unlike ordinary door hinges which affect the appearance, it is installed above and below the door, and has a hidden and practical design. Flexible Rotation: There is a stainless steel ball inside the hinge of the door. The smooth steel ball makes the opening and closing of the door more stable and flexible, and can open and close tens of thousands of times. Easy to Install: The top swivel comes with a retractable pin for quick and easy installation. The hidden turning door pivot hinge can be mounted on the top level of the door and is fixed to a hole on the surface from the door. Widely Application: Concealed rotary door hinges work great for swing doors, murphy doors and more. Excellent pivot clearance option when door weight on traditional hinges of the door frame is a problem.