This is our best value for a small greenhouse packed with features and suitable for most climates. Solar Harvest greenhouses are constructed of a green painted aluminum frame and insulated 4mm twinwall polycarbonate covering.The frame is tubular aluminum which is stronger than any other greenhouse in this price range. The Solar Harvest greenhouses can also be extended to any length by purchasing extensions with the greenhouse or in the future. Instructions are mostly drawings with little text, but the Fast Click system makes assembly quick and easy compared to other aluminum greenhouses.