It fits better than some of the reviewers led me to believe it would. It fits tightly but because it is made of silicone it is thicker, heavier, and very flexible compared with storage lids that are made of plastic. It does not "snap" on, but needs to be "seated" around the edge of the pan. The flexibility and thickness would make it more easy to "bump" the lid off, but not excessively so. I believe it is air tight if it is seated correctly. I assume the the designers made it of silicone because the pan might still be warm when it is covered and silicone is much more heat tolerant than plastic. It should also be less likely to crack with age. I have two insert pans so it is nice to be able to have one in the fridge (tightly covered) and one to use for other meals.Overall I am happy with the lid and would recommend it.