This wire, made in Germany, is made of electroplated tin coated copper strands which give this wire it's superior corrosion resistant properties. Ordinary copper untinned cable is highly susceptible to accelerated corrosion which can break down the strands, loosen connections, and cause connection failures.
The .25mm cable is made with your medium size planes and loads in mind and the .50mm is, of course, for your Giant Scale applications where we are facing high loads and long distances.
0.25mm square per foot
0.50mm square per foot