Collapsible silicone lunch boxes leak. Zip-top ones don't.

Silicone lunch boxes are only leak-proof if you get the zip-top style; the collapsible fold-down kind is fine for dry food but will leak runny stuff.

The collapsible ones (sides fold down, lid snaps on) do save space—empty, they shrink to about an inch thick, so they tuck into a bag nicely. But the lid is just silicone