This is good insulation. However, it is not made for a shorter and bigger diameter heater that one has in a crawl space. For that, you have to patch it together. Tape does not hold very well, so bring your duct tape along when you install.
It is almost a year since I bought the blanket! Hwr, I only recently installed it bcos of the position of my water heater. I measured around my heater w/a piece of cord, and then placed that length of cord on the open blanket. It seemed as if there the blanket was more than large enough and that there would be an overlap. However, on installing it, I found that it did not go all the way around and if I pulled too hard, the outer plastic covering was tearing. Anyway, overall, it was easy to install, and I am pleased w/the final outcome. I have used duck tape to 'extend' the blanket so that both sides can be brought together. I did not have any excess to cover the top of the heater.