I have to say, I bought some stuff off of ebay, "Firemax Heat Lock". $550 for 100' shipped to my door. I was a little leary, and I should have been.
The stuff is junk. I have a bare trail from my burner to the house. -5F and there is water sitting on the ground above it. JUNK! I will be constructing my own and redoing it all this summer. Lessons learned.