These fridge mates are great and I was totally shocked and pleasantly surprised at the difference that they make in how long food stayed fresh and usable. I haven't any idea of why they work, and don't really care how. What I do like is the oblong shape that fits in the fridge a lot better. I seem to have more room the way they stack on each other, and I like being able to see what's in the containers without having to open up every container to find the one that I am hunting for. I like the fact that they do what they say. They keep foods fresh longer and that saves money. The containers are oblong, which is a great shape to go in the fridge and the raised grid in the bottom keeps fresh veggies raised just enough that they stay fresher. I do find the lids to be a challenge but with a little usage, they seem to go on easier. The containers have a vent on the side which allows air to circulate. They are a little pricy but throwing away food is costly. The set that I bought works so well that I plan to add to my set. I would not hesitate to recommend Tupperware Fridgemates to my friends. In fact I have.