Apollo Horticulture 2 Mil Reflective Mylar Sheet Roll - 4' x 50' 2 - Apollo Horticulture 2 Mil Reflective Mylar Roll - 4' x 50' Dimensions: Wide - 48" / Length - 50' / Roll Diameter - 2" Highly reflective polyester film that will reflect approx. 92-97% of light. Increase the intensity of your grow lights without changing the amount of electricity you use. Helps retain heat to keep you room at the right temperature for your plants to thrive.