Metal Structural Bars: This Green House is incredibly robust and firmly supported by powder-coated heavy steel frames Tough Material: PE cover with a crosshatch of green reinforcing fibers throughout. The PE gird cover can protect from harmful rays and bad weather, and give you good solar performance Lightweight and Space Saving: Comes with 4 deep shelves for seedling starting trays or pots, saving space on your balcony and giving you the convenience to start seedlings indoors before moving them outdoors Easy to Assemble: No tools are needed for assembly of the basic structure and shelf. The roll-up zippered door makes watering and misting super convenient Great Starter Green House: Use it for early spring seedling. Perfect for indoor planting and small to medium-sized pots Vivosun green house is supported by a heavy-duty steel frame. Even in undesirable weather, it’s the warmest harbor for your plants. Also, the frame is galvanized, strengthening its ability against rust.