ThriftyVac® Original Mason jar Vac Lids 5-Pk (Wide Mouth with Pump)

They sealed well the first few times. But hard to keep clean enough for consistent seal. I use them on my coffee grounds and so I take off/on every day. I now use a screw on ring to help keep in place and vacuum to keep fresh. That seems to be working ok.

Works great has held up so far.

I purchased this set a couple years ago, and absolutely LOVE IT! I use Mason jars all the time for storing food, as they're easy to see through and I like storing in glass vs plastic. These special lids are perfect for sealing out air, which is what ruins food in a hurry! I freeze soups and sauces right in the Mason jar with the vacuum sealed lids. (Be sure to leave 1/2 inch of space on the top, as liquid expands when it freezes and you'll need some space to allow for this or the glass will break.) The technique is very simple when using these lids. You just place it on the jar with a ring around the lid, and attach the hand pump. You'll know when you've gotten all the air out, as there won't be any "give" left when using the pump. It's super easy to release the vacuum when you want to open the lid again, and just pump it sealed when you're finished. Easy to clean, a fabulous invention!