There are two reasons that the Nano Silver product was changed from 12 parts per million (ppm) to 10 ppm. 1. The difference between the 10 and 12 ppm products were minimal for the user, but most of the clinical tests of the product were done with the 10 ppm formula. The 10 ppm version is very strong, out-performing the competition by a factor of many hundreds. 2. The 10 ppm formula is less expensive to produce without impacting the health benefits to the customer.