The Stiebel Eltron 540002 is a 1 quart flowaide fluid descaler. It is designed for tankless water heaters. This kit is ideal for keeping your tankless water heater in good condition and clean. FlowAide system descaler is an NSF/ANSI 60 certified nontoxic fluid that is suitable to use as a cleaner in your portable water system. The flowaide will help you do this by eliminating mineral deposits from your heating passages and allowing you to extend the useful life of your tankless water heater. In addition, you will also conserve energy, significantly improve its efficiency, and save yourself time and money.