The 6423: Brass Non-Locking Cover Plate, 6-1/4" diameteris constructed of a durable chrome or brass alloy with a hidden hinge for covering existing floor sleeves. A completely flat and safe playing surface is achievable due to the designing of this plate. When in a closed position, all attachment screws are hidden. Standard cover plates have a 5” I.D. with a total diameter of 6¼”. Oversized cover plates have a 6-⅝” I.D. with a total diameter of 8”.