Extension Ring, Box Type Octagon, Number of Gangs 2, Bracket Type -, Capacity 15.5 cu in, Material Galvanized Steel, Number of 1/2 In. Back Knockouts 0, Number of 1/2 In. Side Knockouts 2, Clamp Type -, Number of 3/4 In. Side Knockouts 2, Nominal Depth 1 1/2 in, Nominal Length 4 in, Nominal Width 4 in, Color Silver, Standards File E195978 / CSA listed, File LR-1082, UL 514-A Listed