I bought these because I had been looking for mixing bowls and the lids seemed like such a good idea! I haven't had them for very long yet so I cannot testify to how well they hold up but so far I love them! They are thick glass, and I have never had a pyrex glass product that didn't hold up so I wasn't concerned. It is four great sizes and they are great to be able to pop a cover on and move from cooking to the fridge! 

Pros: convenient, multiple sizes
Cons: a little heavy