Raypak ASME certified heaters feature a metal header design that allows for operation under higher working pressures as required by ASME. These models have a polyester coated, non-corrosive cabinet that is more durable than solventborne and waterborne coated metal cabinets. Every piece of sheet metal that gets powder coated goes through a 7-stage wash system making certain the powder paint has a perfect bond. Underneath the sleek and durable finish you will find galvanized metal that offers superior rust prevention and years of durable service. No need for fans to combat drafting problems. These heaters are designed to draft naturally in outdoor installations with its exclusive low-profile design. It is so thoughtfully and carefully designed it actually protects itself from the things that tend to stifle ordinary pool and spa heaters. It delivers uninterrupted heating performance regardless of your pools indoor or outdoor needs.