Outlet box. 4 in. x 4 in. x 1 1/2 in. Made of galvanised steel. Octogonal junction boxes with BX clamps or with KO conducts are mainly used for commercial lighting and juction applications using BX, EMT or rigid conducts. KO conduct boxes require the use of proper connectors. Extensions are used to add extra capacity to a box, or when installing new wall surfaces.