CAP 2 mil Mylar Reflective Film - 25 feet x 50 inches Mylar is a metallized plastic sheeting. It will reflect about 98% of the light that hits it. Put it on the walls around your plants to reflect wasted light back to the plants. It comes in three different roll lengths and two different thicknesses 1 mil and 2 mil. We recommend the 2 mil for better strength and durability. It comes in 50 wide rolls.