Apeks AT20 Regulator The first stage is a balanced diaphragm design The first stage has 1 high pressure port and 4 medium pressure ports It is designed for water temperatures above 50F (10C) The AT20 has an ergonomically designed control for the venturi that enables you to control the airflow within the second stage at the turn of a lever Comes standard with the Comfo-bite mouthpiece for increased comfort