My newest regulator is a Scubapro MK-20, D-400. The 2nd stage is so light, and the volume of air that it will deliver is so great, that when I bumped it and cause a free flow, the D-400 actually flew up in the air like a rocket. I had never seen anything like it. The free flow was easy to stop by putting my my finger in front of the mouthpiece outlet. I took it down to 150-feet to try it out, and it breathed great. Virtually no resistance and all the air I could want. The big surprise was with the Air-2 octopus. I tried it at 150-feet also, and it breathed darned near as well as the D-400! There are a lot of posts that are negative to the Air-2, but based on my experience I think that it is a superb regulator. If an out-of-air diver were to snatch the D-400 from my mouth I anticipate no problem with using the Air-2 as a back up. I think that Scubapro builds some nice stuff. Pricey if purchased new, but really nice.