APEKS ATX40 / DS4
The first stage is recommended for use in severe conditions (frequent, long dives, cold, dirty water).
This 1st stage has a unique, dry system to isolate the control membrane from the environment. This eliminates the need to fill the water chamber with messy and uncomfortable oils or silicone greases. Instead, air is located in the water chamber, and the ambient pressure is transferred to the control diaphragm via a hard transmitter.