Hubbell-Raco 111 Extension Ring Ceiling Outlet Box, 11.8 Cu-in, 3-1/2 in Dia X 1-1/2 in D, 3-1/2" 3-1/2-inch. Octagon extension Metallic. 1-1/2" deep Side knockouts: (4) 1/2" Cubic inches: 11.8"