Acting as a thin mirror, Sunleaves Mylar reflects nearly 98 percent of available light back to plants where it belongs. This metallic film can be taped or tacked directly to a flat surface or wall. This one-mil Mylar is used to cover a perfectly flat wall. The thicker two-mil Mylar is suited for most other applications like creating room divisions. Each roll is four feet wide. This is a 50' roll.