The pneumatically-balanced ZEO is an engineering marvel of precision, durability and comfort. Its durable chrome-plated marine brass metal valve delivers a phenomenal breathing experience, improves cold-water performance and helps recirculate moisture from exhalation to prevent dry mouth. The breathing adjustment gives the diver a wide range of control to precisely set airflow throughout the dive.The ZEO comes standard with an in-line hose swivel, inhalation effort control, dynamic adjustment technology dive/ pre-dive switch and a super comfortable orthodontic mouth piece featuring an inline ball swivel on the hose connection to eliminate the binding that can cause jaw fatigue.The new cold-forged, over-balanced diaphragm FDX-i first stage is environmentally sealed. The in-line design limits the pressure loss inherent in "L" type first stage designs making the FDX-i more efficient and lighter due to its compact form.