The Wayne Combustion 62390-002 is a replacement Flame Sensor Probe Assembly.  The sensor is applicable for EHG with 9",12", or 15" air tube size and HSG Series Gas Burner.

The flame sensor probe plays a vital role in communicating with the gas valve if it needs to stay open and allow gas flow.  The probe is made of a metal rod and has a white porcelain insulator for heat detection. 

Flame sensor probe failure can be dangerous. 

To prevent any accidents, a replacement is needed if there's a noticeable crack in the porcelain insulator and the probe must be free of deposits.  The presence of these deposits can cause lockouts to your gas-fired appliances.  It can be cleaned with steel wool, emery paper, or extra-fine sandpaper.