This is the Original (standard) size AutoSiphon. The inner tube acts like a plunger, pushing liquid against the check valve at the bottom of the outer tube. This action forces the liquid down the hose to start the siphon. Starting a siphon is as simple as pumping a couple of times then letting gravity do the heavy work. The manufacturer recommends 5/16″ ID Siphon Tubing (sold seperately), we usually recommend at least 5 feet. Saftey Note: Autosiphons are NOT designed to be used with HOT WORT!