The new C370 second stage is based on the capable C350 but with changes, including a balanced valve and a new exhaust tee (similar to that on the S620 Ti) designed to reduce work of breathing. Paired with a proven performer in the MK11 first stage, the little C370 took excellent scores on the simulator at all test depths and breathing rates, and then proved to be a real gem in the water during our test dives.
It took or tied top scores for ease of breathing in normal and face-up positions, and for quiet operation, prompting test-diver comments like “smooth as silk." Some divers found it almost too eager to deliver air with the breathing adjustment cranked full open, as if it anticipated their next breath. Capable and comfortable, selected as a favorite by multiple test divers, and priced below the average in this year's test lineup, the MK11/C370 is our Best Buy.