The glass is very thick and therefore stable and can withstand a lot of. Whether they are suitable as frozen food containers, I do not know, I have not tested it, but otherwise they are optimal and ingenious! The lid close very tightly and are of a robust, stable, transparent plastic. The glass is very well made and precise fit.
So far I had always problems when storing acidic foods such as salads in "Tupper" -Plastikdosen. Often the vinegar dissolved (a mild organic apple cider vinegar), salt or similar, relatively aggressive ingredients, as soon as the filled dishes is a few hours quietly in the fridge, above, where the cooking ends, the inside of the plastic dishes a type level indicator "on. It the plastic surface dissolves blistered off and becomes rough and the dishes is not only dirty, but inside is completely provided with a rough, thin strip, which is probably not very appealing or even hygienic. And, although all companies the Food authenticity and acid resistance is praised. And in view of the discussion of the plasticizer contained and other chemicals that leaves at least an uneasy feeling.
I use the glasses as a butter container, but also to the in a closed stainless steel pot with glass lid and stainless steel steamer basket in a water warming of frozen food, what a steamer and especially the microwave (their influence and often unpleasant change of Sepeisen by microwave radiation is indeed always controversial) easily replaced. The meals are in a few minutes and especially uniformly hot and therefore it is just as fast as the steam oven or in the microwave. Fully equipped with Electrolux gloves (Electrolux 50284163008 Glove Silicone 1x), I also bought at Amazon, of which, however, you have to buy two, because you no pair, but only one gets, but watch out for the left and right hand alike, are easy to clean, you can then take the boiling hot glass easily from the pot.
Even as glass bowls for salads, fruit etc they are very good and useful because they have a large floor space compared to the amount of glass, they are very stable and not tip over.
Thus, the containers are versatile and recommended 100%!