These are perfect; keeping out mold spores while allowing plenty of air circulation. So much easier!!

My homemade jars always took off in the initial stage and slowed down and or stopped later on. It was very frustrating, I was following directions to the "T" and it wasn't working. I began to think that air exchange could be the culprit as it was the only thing left to consider. I bought these counting on them to allow more air exchange and boy did they do the trick. I use these as the lid on the jars and nothing else. It's great to see the jars growing at the same pace through out the incubation process. With the self healing port I don't even use a box for sterility. I wipe the syringe down with alcohol and heat the needle. I wipe the injection port with alcohol prior to inserting the needle and make sure that I have an alcohol swab on the port as I remove it. How much easier could it be!