Pro Strength is a hard water and mineral remover that is a blend of two mild acids and a secret ingredient from the hills of Idaho. It is simply the finest hard water remover on the market. A thick liquid that clings to most vertical surfaces, use it full strength on windows, toilet bowls, fiberglass, shower doors, tile, sinks and more. You may have been looking for the product that was out of Rexburg, Idaho. We were doing the blending in our Boise, Idaho plant for years and when the owners retired, we bought the formula. Nothing has changed other than we put our name on the label.