Fermentaholics Silicone Fermentation Stretch Lids - Waterless One Way Airlock Cap Fits All Wide Mouth Mason Jars - PATENTED Design - 4 Pack - With One Lid Turn Any Mason Jar into a Vegetable Fermenter

Used for one batch. They were easy to wash before I used them. No problem stretching over a standard wide-mouth canning jar. I used 1 quart jars. They feel thin to stretch over something that's pretty big but didn't seem near tearing. Most guys are familiar with this experience LOL. I haven't tried a wider-mouthed jar like some other reviewers posted. They sealed well. I used a glass weight to hold the vegetables under the brine. The pickles produced are good. Try eating pickles with fresh hot rice if you haven't before.

These rubber jar covers work really well at keeping dust and bacteria out while letting gasses and fluids out during the fermentation process. They take a little stretching in your hand first but after they’ve relaxes a bit, they fit and seal quite well over most wide mouth jars! Very easy to use and I’ve used one multiple times and it’s still good to use again!

Only reason I gave it 4 instead of 5 stars for “leakproof” is I didn’t leave enough headspace in my jar and it bubbled up through the vent hole….my fault really!

Good product

1 - the valve leaks and air goes in the jar 2 - it’s easy to dislodge the tiny metal ball inside the valve while you are cleaning the lid. Tiny ball disappears into your sink and the thing now is worthless. So not a durable product.

Very easy to use. They make fermentation projects fun and easy to maintain. I plan to order more next season

Seams kinda flimsy. Just put one on my Fire Cider and will see how it does. I will update as the fermentation process goes.

I really liked these better than the pumps