Synthetic Imported Textile & Man-Made Upper. Removable Mesh Covered EVA Footbed. Durable Rubber Outsole Received APMA (American Podiatric Medical Association) Seal of Acceptance YOUR NEW FAVORITE SNEAKERS: With a winning blend of technical features, the Flex Sierra showcases an engineered knit upper for added breathability and a dual-density outsole, as well as 1st Ray technology for added range of motion under the first metatarsal. Rubber elements andd traction under foot. VIO MOTION SUPPORT is concealed within every Vionic shoe, supporting every step from the ground up so you can confidently move in unmatched comfort. Full biomechanical contact hugs your foot\'s natural curves, providing essential support in all of our casual, dress and active shoes and slippers. Vionic supports you, so you can Walk. Move. Live. With a winning blend of technical features, the Flex Sierra showcases an engineered knit upper for added breathability and a dual-density outsole, as well as 1st Ray technology for added range of motion under the first metatarsal. Rubber elements andd traction under foot.