Fermentation Grommets Pack of 12. Food Grade BPA-Free White Silicone Rubber Complete with 12 Stoppers. Best for Airlocks, Fermenting in Jars and Buckets. 3/8" Center for 1/2" hole

These grommets and plugs truly are of premium quality, as they claim. It's obvious upon inspection - the best I've ever seen. The durometer of the silicone is perfect and the finish very smooth. They work great.Because the axial depth of the groove between the upper and lower sides of the grommet is 1/16", these are excellent for fitting into plastic jar lids of any practical size, Tattler canning lids, plastic bucket lids,etc. They might fit Fido jars and some other bail top jars which have thinner lids. But I haven't tried that combination. For Anchor Hocking bail top jars, which have thicker lids, I found it necessary to order red silicone rubber grommets, which have an axial groove depth of 3/8" from Grainger (part# 3MRR8). On my Fido jars, I used the Grainger grommets because they were all I had at the time.The diameter of the groove recession is 5/8" and that is the size hole to be drilled into the lid (same for the Grainger grommet). I believe going smaller to 1/2" will not only make for difficulty in installing grommet, but also fitting the airlock. Comments?The diameter of center hole for fitting the plug or airlock is, of course, 3/8".Relevant(?) side note: You might find this useful. The Dewalt 5/8" diamond drill bit I ordered from Home Depot does NOT actually measure 5/8" diameter, but rather 43/64" instead - just shy of 11/16". You might be OK with that. I wasn't. It would likely work well enough since plug or airlock would presumably stretch the grommet to fit, but as I had already drilled before discovering the discrepancy, I carefully filled in the gap between glass and grommet with clear silicone, using a toothpick in order to make cleaning easier (yeah, made a hobby of it). We'll see if that actually works. It may be easier to just remove grommets for cleaning in the long run. What I'm saying here is that you might want to try another brand diamond drill and be sure of actual diameter. For drilling plastic lids I find it easiest to use a step drill. Enough already.

These are of great quality; made from a soft and pliable yet tough and strong, sanitary food-grade silicone. I use these in the lids of plastic wide-mouth gallon jars for lactofermentation, with water airlocks. A standard 3/8" stem diameter airlock is easy to insert and remove yet seals well against the grommet, and it in turn against the lid.They fit perfectly in the 5/8" inch diameter holes I drill in the jar lids with a brad point drill, and would obviously also work well in the lid of a plastic pail or the similarly thick white plastic lids of high quality food storage bowls.Once the fermentation cycle is complete, the included silicone stopper seals tightly and lets you store your vegetables, sauerkraut, etc in the fridge with the same lid. I've used regular black rubber hardware store grommets and bark corks before, but these are much better in every way, and will last forever.

I needed a replacement for my fermenter bucket, and I wanted to make some Fido Jars with fernebtation locks as well. I wasn't sure if these grommets would work with the Fido jar since they look a little thin, but I didn't want to wait for an order from Grainger eBay or some other place, plus these are cheaper and include a stopper. These work perfectly on the Fido jar, and give a good snug fit. Takes just a little work to get them on, but not bad at all. The stoppers will come in handy too for storage when I don't need the airlock any more.

I really like these little grommets with stoppers. They seem to be of high quality silicone and are very flexible. I used a 9/16" spade bit to make a ragged hole in the lid of my bucket - should have used a Forstner bit. Inserting the grommet in this size hole took only a small bit of effort, was by no means impossible. I cannot tell yet if the seal is air tight, may update this review later.

So I've been doing a bunch of small batch cabs and pinot noirs, testing different yeasts (ASM, M4, BM4x4, RC212). I buy the 2 gallon white food grade buckets at Lowes along with the 2 gallon lids. On the lids, I drill 1/2in holes, and put these rubber grommets in them. It takes alot of finger strenght to get these grommets in 1/2in hole, but you can do it. With the air lock installed (after SG <1.01), these buckets make airtight seals and bubble away, unlike the buckets from home depot. The lowes lids have a rubber seal in the lid, and home dept does not.You can do the same thing with 5-gallon buckets and lids with these. I plan on buying more.

Good quality product and food grade would buy again from this seller or anybody else who sells this product reasonaly priced. For these 3/8" inside diameter silicone grommets you will need to drill a 1/2" hole in your choice of plastic or metal bottle caps if used for brewing purposes or any container that is used for none pressurized water lines for your hydroponic growing containers for example. These grommets also come with silicone stoppers also and are good when your done with your fermentation. Fermented vegetables and sauerkraut for example. Happy fermenting everybody and take care.

I brew a lot of different styles so dedicating carboy space for cheap hard cider can be a problem. These fit a 1/2" drilled hole in lid of a Tree Top/ Motts 1 gallon juice bottle. Pitch yeast (S-05 in my case), add an airlock and let the magic of time do its work. Bottle the cider and pitch the jug, save the cap for the next batch. Keeps my neighbors in cider all year.Awesome that these come with plugs. These fit all the other sizes of bungs so they are useful for a bunch of tasks but corking a carboy to shake with sanitizer or sealing a carboy while pectic enzymes do work are my top uses.

Okay, I ordered these thinking I'd drill holes into various lids and buckets and such for fermentation exploits. But I was delighted to discover that they fit into my 750mL New Amsterdam bottles perfectly. I can do a secondary kombucha ferment with an airlock, then stick in the stopper and put it in the fridge. A very versatile product, clearly!