Our small and large cold frame greenhouses are made with a sturdy aluminum frame that will not rust or corrode. Molded bottom corner brackets assure greater strength and durability. Side and top panels are made out of heat-retaining 4 mm twin-wall polycarbonate that diffuses sunlight and prevents sun scorch. The hinged top panel provides easy access. Frame assembles quickly and is easy to move. For automatic climate control and improved growing conditions, use the Solar Vent Opener.