This is a clamping lid for gallon-size juice jugs. I wanted to carbonate my home-brew in something larger than a 12 oz bottle, but smaller than my keg. Throw in some free juice jugs (minus lids) from a generous coworker and you have a mid-scale carbonator. I keep them warm in the basement and chill a jug in the fridge when I have company over. BTW: I know that a metal screw on lid with a gasket would be a better solution, but I couldn't find the size online or at my local brew supply. The mouth of the jugs I have is significantly bigger than a 1/2 gallon growler. Thanks for downloading!I've annotated the exploded view of the assembly with the purchased parts and some assembly notes.