I am selling two 4" heat exchange coils made of copper for $150 each. I originally bought these for ported propane tanks for storage but no longer need them as they don't fit how I currently have it set up. The exchange rate I was told was about 23 GPM each. They are over 2 feet long each and finned. They screw into the ports on the propane tanks and have an inlet and outlet. These are heavy as hell, weighing close to 30 pounds each so I will not be shipping. I live in Gray Maine but would be willing to drive in a 50 mile radius.