This is a 90 cm * 90cm * 90 cm pyramidic reflector for solar cooking. Inside there is a 1/3 or 120 degrees of a cylinder wich complete the pyramidic reflector. This part of the sicle reflect almost as good as an parabolics and the design is much simpler. The square 90 cm will collect theoretically about 800 W * 0,8 = 640W of energy, wich is plenty to heat your food. The angels of the pyramid are 60 degrees wich also is matching the angel of the sylinder. The reflector is aiming for a sun 30 degrees above the horizon. For more information see www.solarcookers.ning.com here is an animation of this design: This design