This waterproof poly film is black on the outside and white on the inside. The 5 mil thickness polyethylene film offers excellent protection for heavy weight applications and has outstanding puncture, scuff and scrape resistance. The white surface reflects the light striking it and sends the light back to the plants. The black surface helps block the light from getting to the ground which keeps the weed growth down and the soil warm. The waterproof, light-proof, washable film also helps prevent algae and mold growth. The film also help prevent some insects from attacking your plants. Double it up by putting the black surfaces together to economically and effectively partition off indoor gardens. Very versatile film for your indoor or outdoor gardening use or using as a hay tarp.