Hayward UHXNEGVT12501 Negative Pressure H250fd Indoor Vent Adapter Vertical Replacement Kit for Hayward Universal H-series Low Nox Gas Heaters Negative pressure h250fd indoor vent adapter vertical replacement kit Fits hayward universal h-series low nox gas heater models h150fd, h200fd, h250fd, h300fd, h350fd, h400fd Weighs 11-pound