Product review (5 stars): They're especially great for the older bottles which
These are standard replacement rubber gaskets for Sigg bottles. Even though it says that they're for kids water bottles, they fit regular sized ones as well. They're especially great for the older bottles which, if you've had them for many years like me, have rubber gadgets that have started to harden.

I just wish that the shipping didn't cost as much as the gaskets themselves.