The winebox has since been modified into the square foot solar cooker (Ft2), which is now made with those paste-up square foot mirrors you can buy at the hardware store. The reflectivity is better, and unlike foiled cardboard, they are water resistant. One negative aspect with this new cooker is that the mirrors can break, and the edges are pretty dangerous sticking out there. It is recommended that you put a wood backing on them, or a wooden or plastic frame around the mirrors. It'll run you less than six dollars for the mirrors, and the unit should last a lifetime if it is cared for.