The ATX40 DS4 regulator represents excellent value for money as both the ATX40 and DS4 second stage have both earned their stripes. Both ATX40 and DS4 regulators can be seen at dive sites all around the UK, due to their reliability, robustness and not to mention their superb ease or breathing. The ATX40 second stage is light weight and compact, balanced and features a diver adjustable venturi feature. Matched with the dry sealed and balanced DS4 first stage this package is the ultimate workhorse regulator. The Apeks ATX40 DS4 regulator can be used effectively on singles, twinsets and stage bottles, keeping all your regulators the same helps if you need to change out regs at the last moment.
The best way to configure your ATX40's and DS4's for twinset diving can be found here.
DS4 First Stage
ATX40 second stage