The Mammut Mountainn Trail GTX is a GORE-TEX lined backpacking boot that has a Nubuck leather upper. It features memo foam in the tongue & ankle area for an individual fit, as well as a PU wedge & a TPU insert that provide damping properties & arch support respectively. It uses the Internal Motion-Control system, & has a non-slip Rolling Concept Vibram MT Traction sole. Glossary:GORE-TEX: An extremely waterproof, breathable & durable membrane laminated onto fabrics. Nubuck: Similar to suede but stronger & thicker with a fine grain. It has a velvet-like surface & is resistant to wear.PU (Poly Urethane): Added to products to improve waterproofing, breathability & durability.TPU (Thermoplastic Poly Urethane): A tough, durable elastomer that provides a waterproof coating for fabrics. Internal Motion Control: Prevents the foot from bending outwards or ankles from twisting, & allows for plenty of forward & backwards flex. Also creates support & damping on specific areas of the foot. Rolling Concept: Stabilizes the inside edge of the heel & outer edge of the midfoot, & cushions the outer edge of the heel & inside edges of the midfoot & forefoot. Vibram: High quality rubber soles that are renowned for durability & stability on all surfaces & in any environment.