Instruction: Generate an answer to the question by utilizing the information contained in the document.

Input:
Question: Are containers of this brand air tight and leak proof?
Document: This is a great product an a plastic-alternative storage solution. I mainly decided to go with glass because I didn't feel comfortable heading up soup in plastic containers in the microwave.My main choice for this product is that it was the only one of 30 Good Housekeeping products to pass for air tightness, and you can tell every time you seal these that it's air tight because you have to press the air out of the top when closing.
A LOT of the reviews for this product talk about not being sure how many items came in the package. Mine took a while to ship, but contained 6 containers and 6 lids for a total of 12 pieces. From bad reviews I wasn't sure what to expect, so I was very please when I pulled out all 12 pieces! They arrived well packaged, and in good condition.My containers don't leak. A few other reviewers said theirs did, so I checked with water and mine are all great!
I always hated my plastic container that will stain overtime, also I was always concerned to handle my food in plastic. This is the best container system I found, seal is tight ( even for a soup ) It cleans perfectly and is safe with food.No more plastic for me !
I bring leftovers to work all the time and these are great for heating up food! I was skeptical when I first put the lid on that it would be water tight, but it really does form a great seal and nothing spills. The glass is quite hot after microwaving, but I was so sick of throwing away plastic tupperware when it got the white stains, and melted edge around the top, so it's totally worth it. The two-cup is a nice size and they stack well for storage.
Set is the key word here, it should be 6 containers and 6 lids, because that makes a set.)
These glass containers have a great seal and work well. I'm happy that I selected them. The price is right too.
They are a little costly but I prefer to consider them an investment since I won't be replacing plastic ware all the time. I plan to purchase a couple of the 4 cup containers as well.
I have ordered this several times. The containers are great, but each time I receive the wrong number of them- 4 I got 5; 6 I got 1; 3 I got 1. etc. Customer service has been good though-
These are so much better and healthier than plastic containers for storing food. And the lids seal very well. I even put soup in these and throw them in my backpack to bring to work for lunch without fear everything in the backpack will be coated with soup. And, unlike with plastic containers, I can remove the lid and put the container full of soup directly into the microwave to heat it up for lunch. Lids and containers are dishwasher safe, so clean up could not be easier!
I purchased several pieces of the TrueSeal Food storage containers after reading good reviews about them. I was tired of my old plastic storage containers being stained from food and warped from reheating in the microwave. My new glass containers are perfect for storing leftovers in the fridge. I love the way the lids seal. I am still a little afraid to leave the lids on when warming in the microwave so I instead choose to remove the lid and cover the bowl with a paper towel.
Answer: I don't actually know for sure,but I do believe they are air tight and leakproof because the seal is very tightaround the dish. Just make sure when you wash the seal,to let it air dry completely,or stretch the seal outward towards you to wipe clean&dry.; I had an experience where I didn't  wipe dry the seal and had to throw it out becauseit turned black. But I do think they are good and air tight and leak proof.  Good luck,and I hope this has helped you.