This is a collapsible silicone food storage container that can be used in the microwave. 540ml Mint color I bought it for use as a lunch box, but because it has a steam vent and isn't completely airtight, and because there's a risk of it collapsing during transport and causing a disaster, I'll give it to someone who will use it at home. I took it out of the box, but the wrapping hasn't been opened, so it's unused. Thank you.