I agree, usually the most expensive thing is the tube to surround the electrodes. Fist one I made with a tube the tube was some type of plastic, didn't last long. Think it was the ozone that made the plastic go bad. A better one was made from glass tubing that was for a milking system, but expensive at the time. Don't know the cost today though. The surround tube lets the electrodes used be a longer length, more like in the old Frankenstein movies, a lot of fun as a kid.