Not sure how long this roll of "foil" colored reflective covering (or backing) is, but the box it came in had 250 written on the side of it. Came from a company called Clickstop in Iowa that sells a product (that looks like this one) call EcoFoil, which stops 96% of heat transfer. Hopefully you know what it is and how to use it. A 250' roll of the product sells for $343 on their website.