4" Octagon Plenum Extension Ring, 1-1/2" Deep - Drawn W/Conduit KO's And Fixture Ears 3-1/2" O.C. - Stainless Steel

Plenum boxes are used in air-plenum wall or ceiling surfaces to install lighting fixtures, switches, receptacles or other outlet devices. Square boxes are used to bring power to a number of electrical devices where multiple conductor runs are split in two or more directions.