Cover plates are constructed of a durable brass or chrome alloy with a concealed hinge for covering existing floor sleeves. All attachment screws are concealed when cover plate is in closed position, allowing for a completely flat and safe playing surface. Standard cover plates have a 5" I.D. with a total diameter of 6-1/4". Oversized cover plates have a 6-5/8" I.D. with a total diameter of 8".