I couldn't remember what mil thickness I purchased 9 years ago, so I went with this lower cost option. Judging by feel if this one is 12 mil my old one must have been 14-16 mil. Like I said, that one lasted 9 years, so if I get 3-5 out of this one, I'll be happy. I have an electric heater now, so this is really just for stopping the evaporative cooling and keeping it blanketed at night.
Rating: [4 of 5 Stars!]