This regulator should not be used with very high levels of oxygen, although nitrox in the percentages in which we are likely to encounter it, as in a standard nitrox mix, should not be a problem. The point of this piece of equipment is to reduce weight in your bag, not on your dive. You'll add lead to compensate.
The moment I paid £70 for a few kilograms of excess baggage for a short flight across Europe focused my mind on how important this can be.
There is an option to have the plastic parts in white or black.

First Stage
The MK11 first stage is a diaphragm-type design in titanium with four medium-pressure and two high-pressure ports arranged around a fixed barrel.
This barrel is upright once mounted on a tank, so hose routes are not too tortuous, and there was plenty of room to fit the transmitter for an air-integrated computer next to two other hoses on this side.
The mechanism is sealed against intrusion of water, including any pollution or detritus that might come with it. As such it can be thought of as suitable for use in cold, fresh water too.

Second Stage
The S555 second stage is simple, with only a pre-dive/dive (otherwise known as a venturi plus/minus) switch to reduce the chances of an exponential free-flow at the cusp between air and water. Its control knob was not exactly easy to operate with a heavily gloved hand, but good enough. The body is of thermoplastics.
I should say that the S555 is unashamedly a warmwater regulators second stage, but I got into trouble with the technical director of Scubapro the last time I said that!

Purge Control
Like all Scubapro regulators, the purge button was well defined and easy to locate, even with
a gloved hand. The purge proved progressive, yet very effective. There was never a feeling of enduring a howling gale, yet it cleared the body of the regulator of all water in a moment.

Comfort
The hose was a little on the short side. It seemed to restrict me from turning my head to the left.
Performance was good, compromised only because I had the Atomic T2X, probably the worlds best-performing reg (and much the dearer) on the other side of my tank H-valve.

SPECS
PRICE £679
FIRST STAGE Diaphragm, titanium
PORTS 4mp, 2hp
SECOND STAGE Plastic body
SECOND STAGE ADJUSTMENT Venturi control
WEIGHT 1.7kg
CONTACT www.scubapro-com
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