Very practical

I was a bit skeptical but it was amazing. Best feature is how it blocks water from going into the mask, so even if u dive too deep or water covers the air inlet, there is a ball that blocks it. There will be no air to breath so u will need to go up a bit but at least u won't find water in ur mouth/nose. And you don't have to take it off, once the site inlet is in air, it flows again normally!