Threaded cover for kombucha brewing

Only suitable if you have the same 1 gallon (3.8 liters) jar as I do. It will keep a paper towel tightly fixed to the top of the jar so air can pass but flies cannot. It won't work if you use cloth (unless you cut just a disk).

The optional inner part can be screwed into the cover, so a paper or cloth disk is held in place. This makes opening or closing the jar easy.