Tecnica Women's Viper Low Speed Hiking 100% Synthetic polyurthane and nylon Rubber sole TRS stands for Tecnica Rolling System and it is midsole platform for all our shoes TRS is am energy and cushioning system that provides superior forward energy transfer, comfort and grip resulting in a faster, smoother and safer ride TECNIGRIP outsoles incorporate a rolling spine to provide a consistent grip along with external and center biting lugs for optimal traction and stability Forefoot features our Rolling Rocker that provides better energy transfer and propulsion with every step Ortholite footbeds provide superior cushioning, step-in comfort, durability and are anti-microbial