I designed and built the field box shown on the attached photos around 1972. It is made of sheet steel, about 1/32" thick ( cannot remember the gage of the sheet metal). I repaint it about every 20 years or so. The fact that is is built of welded steel does not make it excessively heavy. I carry the loaded field box plus my transmitter in one hand, and my plane in the other, to get from my car to the flight stands we use at our field. The last photo shows the field box on our field stand with my SPAD Canard plane, for the purpose of perspective.