Product review (5 stars): a little research can save you money
My home is heated with a Heat&Glo fireplace insert.  It is equipped with a thermosensor and a thermopile, to ensure safe operation.  These parts need replacing maybe every couple of years.  The parts are ridiculously expensive from the dealer.  Do your research and save big bucks.  I saw the Honeywell part number on the OEM unit, did the research and found out that replacements were easily obtainable and quite inexpensive.  In my case, the relevant number was the Q313A and everything else was just variations like cable length.  I got the part for about a third of dealer price and it was a direct plug in.