Fully Air Insulated Ring Main Units are built around the Air Break Load Break Switches of the puffer design. These are available in both extensible and non-extensible types. Being modular in design, they can be factory assembled in any configuration based on application requirements. Bus-bars and HRC Fuses being in Air, make it simple to extend and maintain. Cable boxes are suitable for dry type cable termination of either push fit type or heat shrunk sleeve type. Integral cable earthing facility is provided. Features, such as cable fault location testing access, shunt trip coil for remote tripping, are given as optional items.