The stretchy silicone lids fit over just about any drinking glass or cup and create a spill-proof seal. And the travel mug is made entirely from silicone, but still holds its shape thanks to an embedded stainless-steel ring that gives it structure—and that is microwave-friendly for reheats, too.
If you’re not on the silicone bandwagon yet, this material has a lot of good going for it. It’s non-toxic, BPA-free, and dishwasher and microwave safe. It won’t break down with use like some plastics can. And, by switching to silicone, you aren’t creating any toss-away waste.