Not only do the tops not seal things air tight, but the plastic is a poor quality as foods that are typically greasy, to include any meats, seem to stick. I washed the tops repeatedly and a greasy film remained on the covers. Also, the glass seems very delicate and easy to break so I would not advise heavy handling while washing, when placing in the sink with other items, or in the dishwasher.
I have been using plastic recently to store in, however after reading warnings about PBA's I decided I would look for a glass alternative when I came upon this item. I thought I was only going to get one set but after ordering I found it was two. I thought the price was good for the one set but it was outstanding for both sets. They are truly a dishwasher safe, the lids did not warp.
I purchased this set for two reasons-I wanted cheap glass storage containers for food and I'm getting what I paid for. The lids are constructed of a hard plastic and might be hard for some people with dexterity problems to open-the lids are not pliable whatsoever. They will work for nicely for me for awhile.