It mostly functions as described, with some caveats. The caps are silicone, and very floppy. So when you pick up and move the bottles, the flex in the bottle shape can result in a change in air pressure that pops the center flap open.Once the center flap pops open, you can't close it without pulling the cap off to reset it. Becomes a pain. Suggest a more rigid cap body and stronger flap mating seal to prevent.It's close to a good item, but I'll be looking for something a bit better.
Rating: [4 of 5 Stars!]