Brass-plated cover plate includes slotted locking mechanismOpens with simple turn of the flathead screwdriver or coinCover plate consists of 7" (18cm) O.D. brass outer ring and hinged brass capHeavy-duty steel sleeve receives 3" to 3 1/2" (7.6 to 8.9cm) upright and is 8" (23cm) deep1" (2.5cm) clearance required between top of floor and sleeve