Safety Technology International, Inc. STI-9609 Steel Web Stopper, 9 Gauge Corrosion Resistant Polyester Coated Cage, with High Profile, Flush Mount, 4.6" Depth UL listed cage for areas where abuse to smoke detectors is severe Constructed from heavy gauge steel wire with corrosion resistant polyester coating Cover is high profile flush mount Simple removal for servicing the detector Dimensions  8.25 diameter x 4.6H