What's to say about Pyrex except it's just great quality. When it came to purchasing measuring cups it was a no brainer to choose Pyrex. My mother had a set of these and I've used them since I started cooking myself.  I live in a small apartment and storage is an issue so stacking my measuring cups is a must. My only complaint is that the 2 cup fits into the 4 cup perfectly but the 1 cup fits tightly in the 2 cup and has a potential of getting stuck as glass tends to to do. A small issue really compared to getting the quality you do with Pyrex.