These lids work well to provide a tight seal, the silicone is quite flexible. They're a little tricky to put on initially--takes a little practice. The best thing about them, in my opinion, is that they reduce the use of plastic wrap! I would like to be able to buy only the sizes I need. With the bundle I bought, there are some I may never use, but I would like to have several of the sizes I can really use. And, the biggest one is too small for several of my bowls, so I would like to be abl...