Let me jump in here too. *jump* The one I purchased from SOTA instruments has worked very well. It was the only one endorsed by Bob Beck which may or may not be important. Which ever one you end up with, utilize the hot method of making your CS, as it makes a superior colloid. There are two models offered by SOTA. One just makes Colloidal Silver and the upgraded model makes Colloidal Silver and allows you to give yourself blood electrification treatments(another aspect of the Beck protocol).