I drink soda from two liters, 16 ounce bottles and cans; I prefer cans because you get the most carbonation from them. When I saw the Can Convert toppers I sort of knew that they weren't going to work as advertised. Any time you have something that is carbonated as soon as you open it the clock is ticking before it loses its fizz. Even if you reseal a two liter bottle tightly, once it has been opened you have about 72 hours before it is "dead". The Can Convert is supposed to allow you to drink easier from a can. I never had problems drinking from a can so the whole aspect of it making it "easier" seems like a moot point. Any implied ability that this will preserve the carbonation is a complete overstatement. Even the knock-off products that have screw top and flip top lids simply can't provide a tight enough seal to prevent carbonated beverages from going flat. These are good for kids who would otherwise make a mess when drinking out of a can but if it isn't applied correctly to a can (standard sized cans only) then you are going to end up with spills and leaks. My biggest problem with this is the danger of the top turning into a projectile if the open can is shaken or knocked over accidentally. If you prefer to drink your canned beverages from a bottle, save yourself the grief of buying this product and trying it only to end up disappointed and buy your sodas or juices in bottles.