I picked these up at our local World Kitchen to complement the round Pyrex 3 pc set we've had for several years. The larger sizes hold much more then the round containers and they stack better in the refrigerator. I like that they can be used to heat/re-heat in either the oven or microwave. Between these and the round set we were able to eliminate 95% of our old plastic containers. Thanks Pyrex and WorldKitchen!