Sympatex® is the world's lightest, most flexible and breathable waterproof membrane around. It's 100% waterproof and 100% windproof, yet extremely breathable. As a result, feet are kept dry, warm, and comfortable, which is what HI-TEC is all about.
Sympatex® is unique. Unlike other waterproof membranes, it is a
non-porous material providing high moisture transmission which allows
your feet to breathe whilst still remaining dry. Sympatex® is also
resistant to clogging from dirt and oils, so moisture transmission can
continue despite harsh external outdoor environments.