First Stage
The first stage is of a sealed diaphragm-type design with four medium-pressure ports arranged around a revolving turret. It is unusual in that there is a fifth mp port on top of the turret, which might prove especially useful for those rigging a regulator with side-mounted tanks, or anyone with a twin-set whose hose-routeing would otherwise be less than sleek.
This fifth port is cleverly slightly convex and slotted, so that a wrench can secure the turret while loosening a tightly fitted hose.
There are two high-pressure ports let into the fixed barrel of the regulator.
An optional environmental kit protects the unit in harsh conditions. It comes with a standard 300bar DIN connector and an additional A-clamp adapter. The whole thing is finished in shiny black anodising, and represents quite a heavy chunk of metal.

Second Stage
The second stage is connected to the first by a heavyweight intermediate hose, but as I was travelling a long way by plane, I chose to substitute a lightweight braided alternative in a colour-co-ordinated red.
It’s a pneumatically balanced design that delivers gas at constant pressure independent of what’s in your tank.
There is a venturi plus/ minus switch that can be used to resist exponential free-flows at the surface,
and a breathing resistance adjustment knob.

In The Water
There is a big exhaust-T, and bubbles were routed well away from my face, but now that I’m used to the more fashionable compact exhausts found on most other regulators, I discovered this was slightly annoying where it sat on my chin.
The purge button was easy to find, and gave a controlled and graduated effect.
The 3100 gave me sufficient gas when I demanded it but, compared to the superb alternative regulator I always carry with me on trips (also a US brand with a fifth port and made using lightweight titanium), it provided a much wheezier breathe.
I could easily have soldiered on with the Dive Rite 3100, because there was nothing really wrong with it, but after a few days I dug the other model out and used that instead.

Aqua-Lung Legend Supreme, £380
Hollis Tech 212 DC-1, £375
Mares Abyss, £349

PRICE £345
FIRST STAGE Diaphragm-type with turret
PORTS 5 mp, 2 hp
SECOND STAGE Pneumatically balanced
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