Free Flex is Bryan Boilers� newest Ultra High Efficiency condensing boiler. �Free Flex is built with Bryan�s exclusive flexible watertube heat exchanger, but now in a stainless steel design with a competitive installed footprint.� Other features include: 1000 to 3000 MBH input, AHRI Certified at 95% Thermal Efficiency, fully field repairable, a Lifetime Thermal Shock Warranty, and Variable-Primary or Primary/Secondary piping.