It's made of silicone and you just set it in your pot when you're boiling something that tends to boil over. Now it seems silly - but when you cook a lot - it's a pain in the butt when things boil over!!
Here's a shot of it in action! Handy huh? These lids are really affordable too - you can get this one for under $15!
The ring in the middle is also nice because you can still stir while it's on your pot. Because of it's design - it also fits a wide variety of pot sizes. I can't believe they didn't think of these sooner!
It's great because you set it on top and now you've got a lid for all those bowls that don't have lids!!! This is great for leftovers in the fridge and for outside events. They even make them in little sizes for drinks so no bugs get in!!
Here's a few other of their products to give you an idea of the size. They are so handy to have around - I never can seem to find tupperware for leftovers - so it's great to just have a lid that I can pop out and know that it's SEALED! I think the designs are really cute too - they have lily pads, hibiscus, sunflowers and more!
Disclosure: I received one or more of the products mentioned above for free using Tomoson.com. Regardless, I only recommend products or services I use personally and believe will be good for my readers.