The A700 second stage, with its metal casing, screw-down casing cover, metal valve housing and over-molded accents, exhibits a real muscularity in design. Its air-balanced valve technology and oversized exhaust valve work in conjunction with a well designed sectional exhaust tee, a first-rate purge and responsive user controls to create a bullet-proof breather with effortless inhalation and an ease of exhalation that is unmatched.