Can be matched to a blower module for a heating only system or it can be matched with a blower module and cooling module for a system that both heats and cools;Slide in hot water coil is supplied separately;22 gauge galvanized steel construction;Easy snap latches;Corrugated aluminum fins mechanically bonded to copper tubes;Tubes are 1/2" diameter on staggered centers;Each system is pressure tested at the factory;Full-collar fins provide greater tube-fin contact for excellent heat transfer