Scubapro A700 second stageThe A700 second stage, with its metal casing, screw down casing cover, metal valve housing (barrel) 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. A700 Second