Black Wire ESP Exhaust Thermistor Probe Replacement for Harman Pellet Accentra FS (Accentra Cast) Accentra Insert Advance P38 (P38+, PP38+) Invincible Insert Invincible RS P61 P61A P68 PB105 Boiler PC45 PF100 Furnace XXV (25th Anniversary Model) Black Wire ESP Exhaust Thermistor Probe for Harman Wood & Coal DVC 500 Mark I 44 Magnum Black Wire ESP Exhaust Thermistor Probe for Heatilator Pellet BA100 Replacement Part Number: 3-20-00744, 1-00-00744, and 3-20-11744