NTI Boilers Watertube Boiler 93.7% AFUE 5:1 Turndown, 300k-Input, 251k-Gross Output, 180 lbs, Water Content-2.1 gallons, 1-1/4" FPT Heating Connections, 1/2" NPT Gas Connection, 4" Vent Size, Dimensions-21-5/8"D x17"W x36-3/8"H