I've dove the mc9 in so cal water temps down to high forties, it's a decent regulator, but ultimately I switched to scuba pro, because I only seemed to get about 80 dives out of the cressi before it started breathing poorly, and getting it serviced, was expensive! It was during one of those services I borrowed a friends scubapro mk25, G250 combo, it breathed like butter! I switched and haven't looked back , I picked up a used MK17 (perfect for cold water), and an old G250 for about $175 total and had rebuilt as my primary, and then picked up an mk10, and another G250 for a total of $100 for my pony.....these regs are bulletproof, very affordable, and can't really imagine any regs breathing better