Oh, so sorry that happened to you. Mainstays is a Walmart brand. They do have the reputation of buckling and deforming. There are older threads about them on this forum.

I've never used the Mainstays brand flats and will stay away. I do buy their rolls of vacuum seal bags and find them acceptable.

Did the lids still seal? As long as it sealed you're ok , just looks sucky.

I had a Ball lid that did like that but it still sealed.

HU

I posted, to just let people be aware.

Yes, I knew there are some old posts about this... but these lids were brand new, never before used... only, I am not sure, when I bought them. Either 2018 or 2019.

I like new info, without wading through old posts.

Yes, two out of three sealed. I marked them with a BIG red X on the lid... so I will use those up first. The one that didn't seal is in the fridge. It will be empty within a week.

I tossed the rest of the lids. Not sure, why I used them... as I also had two boxes of Ball lids. At least, now I know.

I haven't canned much the last two years, but had planned on canning more... only, I ate most fresh as I picked this summer. Will have to get me a pressure canner, so I will be able to can other produce in the future. Just didn't want to order and hang there waiting for something that wasn't coming in. I did that long enough for elastic for sewing masks.

This has turned in to a really sucky year overall... the worst for me in the last 10 years. I am hoping to make the best out of everything that has been tossed at us, and take measures, to have a really successful garden next year.

Moni

I have read that the buckling happens if you put the rings on too tightly