The Poseidon wing and harness system has been made specifically to fit the Poseidon rebreather. However, If you choose a different wing and harness system, the Recreational Counter Lungs will be compatible.
The inner bladder of the lungs contains the gas you breathe through the loop. The outer lung is there to protect the inner lung and is made with a reinforced tough nylon material. The lungs are fitted with a big D-ring in the bottom of each lung, where you can attach bailout tanks, lights, SMBs or anything else that may come in handy during your dive. The inhalation counter lung has a Velcro strap fitted on the side where you can attach your inflator hose. The exhalation lung has an Over Pressure Valve fitted on the lower part of the lung.