This Resisto W1R 55921 reflective single bubble insulation roll measures 4 feet wide by 125 feet long, covering 500 square feet, and features a white surface on one side. It is constructed with a single layer of polyethylene bubbles encapsulated between highly reflective metallized surfaces or a metallized surface and a white surface. The insulation primarily functions as a radiant barrier, reflecting a high percentage of radiant heat to reduce energy transfer and costs by preventing heat loss or gain in various environments. It also serves as a vapor barrier, helping to control condensation and air infiltration. With a thickness of approximately 3/16 inch, this lightweight and durable insulation is Class 1/Class A fire rated, meeting ASTM-E84 and ASTM-E2599 standards. It is designed for easy installation in residential, commercial, industrial, and agricultural projects such as pole barns, metal buildings, attics, crawl spaces, and ducts.