Depends on exactly what you want to do and achieve! If its price then little units like the SOTA, CSG/TS2B1 etc. If you want to make serious Colloidal Silver then you should go for the CSPRO model. Alot of people go on about these SG-6's and Colloidal Masters but the best for your money with performance and speed with quality is CSPRO's powerful baby. You won't make Ionic with these generators.