The PVC sight glass will melt with higher temps. I tried keeping it in line while I was using my CFC to cool while whirlpooling in my kettle. I now have a new one and a spare.
It serves it's purpose well to monitor the wort flow from my CFC chiller to my fermenter and to give me an idea about the flow of 02 entering the line.
All in all, well worth the money.