I've only used the bigger ones for storage & iced coffee. (shaken, not
stirred)

: - )

Now, Classico does sell a pesto sauce in a smaller jar--we use it as a
base with white sauce on pizza because I can't eat tomatoes. I have
re-used those little jars for jams, jellies & butters in a BWB--no
problems with breakage or sealing. I haven't had a issue with the
shape of the jar because I usually do small batches and they fit okay
in my granite BWB canner.

HTH