This is a good used Carrier, Bryant, Payne 1 3/4" plastic upper " Burner" indicater sight glass in great condition. 
Carrier part # 323018-201.

If you need this part you may need it fast. We will ship immediately after payment clears. Contact us if you have any questions. 

If any shipping options are chosen other than our free shipping, those funds will not be refunded for any reason if the part is returned.
  
Carrier also uses a 1 3/4" sight glass on the lower door for the "control board".  They are not interchangeable. See Ebay item # 275073787505.