I got a silicone cup cover from Epcot park five years ago and just started using it in college. It is a great way to keep drinks a little warmer and safe from spilling. The suction on the top is apparently very strong even though I have never tested it. My main use for it is to make cup ramen and it honestly makes it so much more fun. Tiny products like these are simple and cost almost nothing to produce but will sell because of how much they brighten up boring tasks. They also make these in larger sizes for refrigerating bowls and plates, as well as for covering pots. This design is such a simple and smart solution to saran wrap for refrigerating food because it is more secure and less wasteful.
