The size of the containers are great. I usually use the smallest container if I want to pack a lunch and bring it to work. The other sizes (3 cups, 6.3 cups, 12.7 cups, and 21 cups) are great for bigger fruit/vegetables (or meals). I have only used the small one in the microwave and it was for a very short time, so I am not sure if I may experience the problems others have if I were to put it in for a longer amount of time. Likewise, I have noted that the air valve function does not always work perfectly. Sometimes air doesn't want to come out or finds a way to escape in. I've only experienced this to a small extent, and my food still was fresh after a few days, so this was not a big problem for me (just something to be aware of if you have more sensitive/delicate products in the containers).
These containers also come with an instruction guide that explains how to use this air valve, which was very helpful. I like that the containers are BPA free and the lids have four snaps (on each side) to secure freshness and prevent unwanted spillage. The containers also have a wave pattern at the bottom which prevents moisture from getting into fruit or veggies and allows them to last longer in the containers. Although there are minor problems to be aware of, this is a great set overall to have. If you accommodate based on the "less-than-perfect" qualities, then I believe you will be quite pleased with these containers.
Want to check this out for yourself? Here is the Amazon product link:
*I received this product at a heavily reduced price in exchange for my honest and unbiased review*