True, but then you’ve only got like three different sizes possible, because you can only change the depth. There are not going to be a ton of glass options that fit this description because glass containers that stack like this tend to get stuck and can break so much more easily. That’s why it’s easier to find plastic containers that work like this. It’s even a problem with restaurant grade pint glasses which are nearly indestructible. Ever had a stack of those little devils decide they are better together? Such a pain to get them apart. Next time you’re at a bar notice the pint glasses. Most places won’t store them stacked because as the cool after being put away warmer from washing they have a tendency to get stuck. It happens with Pyrex measuring cups too. Plastic can be wrenched apart. Glass can be too, but sometimes it makes big giant mess. Stacking glass containers that are all the same size inside of each other makes them significantly more susceptible to shattering as the expansion and contraction with the temp change as well as the extra tight banging around is just not a great mix and makes stuff break so much quicker.

I have seen some glass that has silicone on the outside which would help a ton, but those seem to be bested still. Maybe some company out there makes stacking ones? That could be a possibility. I just haven’t found any.