NTI Boilers Watertube Boiler 93.5% AFUE 6:1 Turndown, 150k-Input, 136k-Gross Output, 100 lbs, Water Content-1 gallons, 1" FPT Heating Connections, 1/2" NPT Gas Connection, 3" Vent Size, Dimensions-18-5/8"D x17"W x29-7/8"H