These shoes are designed to push air throughout the shoe to reduce humidity and keep feet cool and dry. Natural cork, wool and leather insoles wick moisture away, while providing excellent arch support. Sole is made of natural rubber from trees IMPORTANT SIZING INFO: ***Mephisto fit a bit large, but this is done by design, as most Americans wear shoes too tight. After a short time wearing Mephistos, you will understand that they should be a bit larger than what you are used to.***