I have no clue why how I didn’t find these sooner! These silicone sippy lids are completely genius! These lids fit over any glass or cup instantly making them spill proof! They don’t include any extra valves or parts so they’re very easy to install. I love that these lids are made from FDA approved 100% food grade silicone so I don’t have to worry about my daughter chewing on the spout! Of course I was a bit skeptical at first, but after testing them out myself I was very impressed. The lid fits openings from 2.5 inches to 3.75 inches which is basicly any normal sized cup. This means I no longer have to carry around spare sippy cups in my daughter’s diaper bag when we go out to eat. I can simply pop one of these onto the restaurant’s glass and we’re good to go. The only cup I find that these lids DO NOT work on, is disposable plastic cups. Since the lid is so tight to prevent leaking, they tend to bend plastic cups. Other than that, these are a MUST HAVE for on-the-go moms!