MARES 28XR FIRST STAGE- XR LINE REGULATOR DINMares fitted the 28XR first stage with the very best in modern regulator technology. It uses the innovative balanced diaphragm concept, which is operated by a double piston, all ecologically sealed using AST Auto Sealing Technology. This also guarantees a perfect seal against the possible entry of sand or particles, especially in cave diving or in polluted waters, also giving the diver the possibility of removing it in the water without flooding it.