Back Counterlungs for Poseidon MKVI and SE7EN Rebreather.
The novelty of Poseidon, after continuous requests from its users users underwater rebreather!
Undeniable and advantageous features compared to the front lung bags are:
 
the diver's chest is completely free and this allows an optimal reading of all the instruments;
total management of the bailout cylinders and the suit's exhaust valve;
best horizontal posture in the water, without any effort;
the manual DIL and O2 injectors are positioned (adapters sold separately) on the T valves and can be easily reached underwater by the diver;
the lungs are provided with holes that make them ready for the installation of any MAVs (Manual Add-On Valves) at the discretion of the diver to bring only the blocks for injection in front and the insertion of an offboard gas in case of need.