C.L.
Hi B.! Thanks for asking your question.
Even though measurements might suggest that "something will fit", we all know that in practice this is not always the case. Since it appears no one else has used these to systems together, you might be stuck with testing it out for yourself.
If it was me, I would decide which of these two systems (the lunchblox or the flip-top lunch box) I would much prefer to use. Then I would take that system to a store where they sell the second and just play with it to see if there is a configuration that will work. (If you're really lucky, you'll be able to find both items at the same store, and not have to buy anything until you've "played" with it.)
As a reminder, when it comes to containers, the abilities of children does not equal the abilities of adults. I always have my daughter try to open any container I will send with her for lunch. If she can't easily open it, I don't buy it. If she can't zip/unzip on her own, I don't buy it.
Good luck, and please let us know your thoughts and findings. I was eyeballing the lunchblox just the other day, but wasn't sure if they'd work for us or not.
To everyone else.
How incredibly rude some of you are. This is a community where people ask questions of other people to guage their experiences. Yes, B. can go measure for himself. But just because something "measured" doesn't mean it actually works. B. was just asking if anyone has used these together... and if they have whether it worked or not.
Have you never bought something because the measurements suggested it would fit, only to find that the opening was too small or you couldn't pull the top up over the contents. "Fitting" and "working" are two different things.
I'm appalled that you would treat a community member with a legitimate question in such a way... whether that community member is a mom or a dad.