It is for glasses with a very thin spout! It is very difficult to fit into a plastic cup with a slightly larger spout, resulting in spillage of the contents!

Nice idea but the material is not elastic enough to fit different glasses, which makes it useless. I had it permanently in the stroller bag in case I forgot to take their cup or if we lost it, but in the end, I only needed it 1-2 times and had to search for a specific-sized glass to use it.

In the negatives, I put their prohibitive price. Too expensive! However, they also have their positives. I saved myself from constantly cleaning up my son's spills! Every time he drank milk, water, or juice in a glass, everything would be a mess (couch, floor, etc.). With these lids, I literally saved myself! Of course, a small amount still spills from the big and small holes, but it's nothing compared to before. I recommend it to all parents with difficult and worried children who love sippy cups!