This is a HTP Pheonix 316L Stainless Steel Gas Fired Water Heater. This heater comes with a tank 55Gal, and is constucted of Stainless Steel material. The heat exchanger is constucted of a proprietary 90/10 cupronickel and 800H stainless steel mix. The heater vents in your choice of PVC, CPVC, SS, ULC S636. The turndown ratio of the heater is 5:1, with an efficiency of 0.95 . The heater is rated for a first hour of 295Gal , and a rating of 229 with a 100F Rise.