Holllis 500SE Second Stage's redesigned, pneumatically balanced servo controlled valve delivers superior performance.
Even the tiniest, gentles inhalations kick-starts the valve as air starts to flow into the second states creating a vacuum behind the diaphragm, drawing it inward and rapidly opening the valve even further.
The mouthpiece is one of the most comfortable ones there probably is, which means less jaw fatigue on longer dives.
The exhaust is conveniently placed, directing the bubbles away from the face and vicinity. You can also use the second stage which ever way -there's no 'up' or 'down'.
Please note: this is the second stage ONLY and comes without a hose.