Hayward FDXLTER1930 FD Thermistor Replacement for Hayward Universal H-Series Low Nox Pool Heater Replacement fd thermistor Fits hayward universal h-series low nox pool heater models h150fdn, h150fdp, h200fdn, h200fdp, h250fdn, h250fdp Also fits hayward universal h-series low nox pool heater models h300fdn, h300fdp, h350fdn, h350fdp, h400fdn, h400fdp Weight 4 pounds