A few years ago I went to a DUI Rally. We arrived a day before the rally and couldn't wait, so we went in for a dive. We came to the surface, and as I was going back down I got my first sinus squeeze! OCEAN REEF was also at the Rally letting diver's try out the full face. My buddy and I tried it out because the Rep went with you. We figured if I got my "squeeze" again he could go on with the Rep. I did not get any and the Rep was nice enough to let me use the mask for the rest of the week end,and I did not get any more squeezes. A few months later I bought one. Well worth the money. No "clearing the mask", no fogging up, no teeth or jaws hurting, and I stay a warmer in colder water.