The Oso models are tried and true trail sandals. The Middle Bear features a super aggressive and durable Vibram tread, a flexible sole, and our patent pending Winged performance laces. Our patent pending Wing design allows for the simplest, most secure and intuitive LUNA experience yet! Wings keep your LUNAs securely in place without the use of a tech strap, while maintaining total lace adjustability and optimum comfort. Made of a flexible, smooth and very durable material, Wings are made to move with your foot and stand up to the gnarliest conditions.