Are they the same as the Ball flats? I just found a full dozen freezer jam jars *with* plastic lids at Goodwill, was looking on Ball and Bernardin website for lids (I think my cousin has 3 she's using as juice glasses b/c we couldn't find any lids when we cleaned out the farmhouse basement). I saw Bernardin makes snap lids but they look like standard flats you use with screw-on bands.

Has anybody used these as freezer (jam or other) jars? Do the lids stay on or do they tend to pop off even if you leave enough room for expansion? They look a little flimsy to me - but might seal better than the plastic screw-on lids (which always leak in transport when I use them for fridge storage).