Yeah, 9999 silver rounds are the best because you are 99% sure they are the finest silver available to use. I have seen many sites on the net posting that they sell 99.99% pure colloidal silver wire but I have my doubts and believe that many of these sellers are actually selling 925 wire as pure. See 925 wire is way easier to get and way more abundant commercially. 925 wire may also be more harmful to you then beneficial depending on what its mixed with. Either way you never want to make colloidal silver with anything less than three 999's!