The Spectrum Series boiler is now available with an optional stainless steel jacket, which is designed to provide corrosion resistance for indoor or outdoor installations. The boiler features a reversible, two- or four-pass heat exchanger made from commercial-grade 7/8 in. I.D. finned copper tubes which are extruded from the tubing to ensure maximum heat transfer efficiency. The units are available in sizes ranging from 100 to 400 MBh.