Design and Materials
Surface boxes are divided into groups based on how many devices they can hold and how wide they are. Dual devices, such as a straightforward lighting switch, switch plate, and socket, can fit inside a one-surface box. Fiberglass, plastic, iron, steel, and aluminum Metal-clad cables and indoor conduits work best when used with steel surface boxes. When the cables are sheathed in non-metallic materials, the surface box is built from plastic or fiberglass. Typically, outdoor surface boxes are made of plastic, iron or aluminum.