Stainless steel (201/202/304) and galvanized steel look similar, and it can be difficult to distinguish between them with the naked eye. This product is a "galvanized steel identification liquid" used in metalworking and DIY settings. When applied directly to the target area, galvanized steel will turn red, while stainless steel will not react. It is a small 12ml size, making it convenient for carrying and on-site verification. *The product has been opened once for photography. Please be aware of this. *We will respond promptly. We can ship it by the next day at the latest, so please rest assured.