or, for that matter, any unsealed first-stage, are inappropriate for ice-diving conditions. Period, end of discussion, game, set and match.
SP has waged a TEN YEAR war on this front and has not yet "won". They never will win, other than by packing the first stage with grease, which works but sucks in terms of contamination getting in there and makes a rebuild a REAL mess of a job.
Now the new Mk25s (just saw one) have this thing that looks like the borg just above their turret - the latest attempt to get more surface area near the big end of the piston and keep the water in the balance chamber from freezing.
The simple fact of the matter is that all this claptrap, including the insane bushing frenzy and composite piston garbage that SP has engaged in over the years, is crap.
Its pure, unadulterated crap!
SP makes a diaphram first. If you want to dive in water under 45F or so, use either it (sealed, of course) or a suitable sealed BD regulator from a different manufacturer.
No piston reg is truly suitable for those conditions.
If you do not want to dive in those conditions, then the SP Mk10 is one of the best-performing regs available, is quite cheap on the second-hand market, can be rebuilt by a monkey in his sleep, and other than the turret bolt (which you must not overtighten and darn sure should use a torque wrench on) and the seat (which is a "custom" part) the rest of the reg uses standard, off-the-shelf O-rings which you can replace with EPDM parts (oxygen compatable) for about FIFTY CENTS A REBUILD.
I own several Mk10s and am always on the lookout for more in reasonable condition - they work well with virtually any second, are simple, work well, and outperform 90% of the other crap out there.
And by buying on the secondary market I give SP - who is one of the worst in the business when it comes to the price-fixing games - exactly nothing. Nor do I need their "rebuild parts" for most overhauls; the only exception to that is if I need a new seat.
