For my application, they did not work. I needed something to help keep my homemade sparkling water fresher than placing a piece of plastic under its regular cap. The problem was, these were not big enough in circumference sooner, so when I placed them in the hole, they were nearly flush with the opening. But the worst part was after sitting for less than a minute, they would pop off, like a cork on a champagne bottle!  Funny, but not workable. They work perfect for wine bottles though.