I think the hardware is 3/8th inch. A 1/2 inch wrench fits the nuts and bolt head. Could be 5/16? Assemble it by trapping one nut in the baffle with the nut trap, thread a second nut onto the bolt and thread that into the trapped nut. Then expand it in the container till tight and lock it in place with the second nut. You can get a wrench on it but you will have to flip the wrench repeatedly to get a grip on the bolt end because of it being in a jar. There is a slightly taller version of the file for a larger container. This is part of my wind powered rock tumbler design but is useful in it's own right for other tumblers. Use a cut up piece of 100 grit sand paper and some water for the rough polish and 1000 grit with water for the fine finish. Don't bother buying those expensive bags of grit available for tumblers. I've included the Sketchup files so you can adjust the design for your container using the Push/Pull Sketchup tool.