VIVOSUN Horticulture Highly Reflective Mylar Film Roll 4FT x 100FT 2 Mil This highly reflective film will reflect approx. 92-97% of bulbs' light. It is durable, puncture and tear resistant. It increases the intensity of your grow lights without changing the amount of electricity you use and also helps retain heat to keep you room at the right temperature for your plants to thrive. The 2 mil grade is the most durable available and this unique design boasts a poly backing which acts as a vapor barrier. Heat Resistance Temperature: 190 / 374.