This thermal conductivity demonstration cylinder measures 200 x 30 mm in diameter and is constructed so that one half is wood and the other half is metal. The two materials are joined end-to-end to form a single cylinder. When paper is wrapped tightly around the cylinder and the rod is held above a flame, the portion in contact with the wood will quickly scorch while the portion in contact with the metal remains uncharred. This dramatically demonstrates the difference in thermal conductivity between the two materials.