Air to Water Heat Exchangers also called Water to Air Heat Exchangers. It's designed with high-quality aluminum fins and seamless copper tubes. Despite a fin density of 12 fins per inch, there is low flow resistance. Our models, ideal for both residential and commercial applications, can be used with a boiler or any other indoor/outdoor source of hot water to transfer heat into your existing forced-air systems, such as indoor boilers, outdoor wood boilers, natural gas boilers, propane boilers, oil boilers, electric boilers and other hot water heaters or furnace heat exchangers. This particular model has 1" ports and a capacity of 60,000 Btu. This product has a 1-year warranty against manufacturer's defects and is ETL listed.