The Burnham 204NC Natural Gas to Liquid Propane Conversion Kit is suited for Series 2 Standing Pilot Boilers. Since it's introduction, the Series 2 has earned a reputation for safety, reliability and durability. With a robust cast iron heat exchanger, long lasting stainless steel burners, quality manufacturing, and over two million installed in North America, the Series 2 is one of the most popular choices for those seeking a reliable, long-lasting gas boiler.