Pennant, Tube Assembly, Heat Exchanger, 1750, Code Compliant ASME Heat Exchangers, Built in accordance w/the requirements of the ASME Boiler and Pressure Vessel Code, Individually serialized w/H-4 data reports on file as required by section HG-520.2 and HG-53l, Copper tubes and glass lined headers, ideal for hydronic or other closed loop, low oxygen content systems, Performs well w/normal water (7.5 to 17 grains hardness) in volume water applications.