Mylar 50" X 25' Roll Heavy Duty 2 MIL. Used to reflect misguided light back onto your plants. Reflect: 1. To throw or bend back (Light for example) from a surface. I tell customers that it has been my experience that the dirtiest Mylar reflects more light than white paint or plastic. People respond to that comment with quotes from book authors stating a different opinion. My response is simply asking the customer, "how many times have you seen your reflection from a newly painted wall”? If the paint is so reflective, then why can’t you see your image from the light reflection the way you can with a mirror or Mylar?