Manufactured by Riverstone patio furniture. Not all greenhouses are made the same and the line of greenhouses by riverst industries proves to be true. is applying good old ingenuity to make the best product for clients and help to elevate the standards of all greenhouses. the highest quality extruded aluminum grade not the thinner and more brittle foreign aluminum and electrostatically painted black to contain. % lead, greenhouse uses on average more than more aluminum than the average imported greenhouse. Why is important. weaker the framework the less snow the greenhouse can hold in the winter time before collapsing on itself the easier it will be get damages in wind. While most hobby greenhouses on the market us less high-priced thinner walls and roofing materials the crystal clear walls are as thin as. mm, the uses professional grade mm twin wall polycarbonate. is the same thickness as used in the commercial greenhouses. twin wall polycarbonate acts as a double pain window keeping cooler air in during months and in.