Rubber sole Seamless Mid-top Knitted Wool Upper:Superior comfortable & breathable sock-like texture delivers greater elasticity, naturally hug the foot and traps heat to keep feet warm. Ergonomic Design: Loose-toe design prevents pinching and blisters, perfect for all-day use. Double Widened Elastic Straps: Perfectly fits the shape of any foot, especially good for high insteps. Spain Elements Outsole Design: Artistic and thickened, anti-slip outsole brings a better walking experience. Ultra-lightweight Design: One-piece design weighs roughly the same as an avocado (17 oz/pair).