The back mounted counterlungs has a total volume of 8 litres.

The counterlungs consists of the lungs itself, two swivelling T-pieces and an automatic overpressure valve that can be operated manually.

The T-piece located on the left shoulder of the user (diluent side) holds the ADV (Automatic Diluent Valve) and the T-piece on the right shoulder of the user (Oxygen side) holds the inlet for manually inflated oxygen.

The protective cover of the lungs is made from a sturdy and abrasion resistant nylon.