Gas Fireplace question

[Plumber69]

Has a Efel freestanding gas fireplace. It has a say 1/8 copper tube from gas valve to underneath of fireplace then increases to about 1/4" x 4 inches long. Im sure its probably liquid filled. But in not sure what it's purpose is. And no its not the thermal couple

 

[WorthFlorida]

This is from the gas fireplace gas valve to the fire box? Is this 4" piece you provide or comes with the unit? It might be an orifice or just an adapter to make the connection to the fire box from S.A.E. to metric.

 

[Sponsor]

 

[Fitter30]

Is this what you have?
https://www.google.com/url?q=https:...FjAJegQIAhAB&usg=AOvVaw16TpcTGgsAAQC4ibKCtK93