A200 Boiler Treatment - Has been specifically designed for outdoor and indoor wood boilers with mild or stainless steel construction.  This product may also be used as a full spectrum water conditioning agent for other hydronic and solar heating applications. A200 is the only environmentally friendly boiler treatment. One quart treats 200 gallons. Buying 2 quarts at a time saves on shipping... long shelf life so you're ready for next year!