Why do you often refer to the rust sealers as just "Silver"?

Silver is the color of both rust sealers, Original and Slim. When we first started in business, we only had rust sealer and the black chassis finish coating. We referred to them as the "silver" and the "black". However they're very different from each other--the silver is the much more effective rust sealer and the black chassis finish is better as a topcoat.