This Titan Greenhouse series is called "Harvest Premium", is designed with the 4 SEASON GREENHOUSE gardener in mind. 10MM Double Wall Polycarbonate gives you the best protection from the cold and to retain heat. Compare this to the other Greenhouses for sale for the value and quality, there is no comparison. Greenhouses in this price range are 4mm thick polycarbonate vs our Harvest Premium at 10MM thick Double Wall POLYCARBONATE, ours is 2.5 times thicker. It's the best and strongest greenhouse in the world market.