Hubbell-Bell 5363-0 Round Weatherproof Extension Adapter, 18.3 Cu-in, 4 in Dia X 1-1/2 in D, Gray, 4-Inch Extension adapters are used to increase box capacity and allow the installer to add "take-offs-Inch to new boxes/devices Rugged die cast construction Reinforced connector outlets State-of-the-art powder coat finish Includes four closure plugs