It comes with a lid to help maintain freshness and keep out odors. It's made of food-safe silicone that's BPA-free and dishwasher-safe.
Promising review: "This is the best invention since sliced bread! How many times have you thrown out soup that you forgot about in your fridge??? Well, say goodbye to spoiled soup! Finally, a way to store measured quantities of broth, but I love to use mine for soup and...wait for it...SMOOTHIES! These cubes are the best for freezing measured quantities of smoothies, simply throw one in the Vitamix, and boom! You have a fresh, already icy cold smoothie for breakfast or a snack! For anyone with limited freezer space which, let's face it, is most of us, this is a real gem. I was a bit worried about how easily the cubes would slide out, but no problems at all! The best part is how easy the cubes store in a gallon sized ziplock bag so you can reuse the cubes. AND they are dishwasher safe??? Souper Cubes, why did you take so long to come into my life!??! I can't wait until the holiday season so I can gift these as stocking stuffers — to anyone I know, you now know your gift." —jane s. catalano
Get it from Amazon for $19.95+ (available in three sizes).