Manmade,MeshImportedSurface: Road. Differential: 12 mm. Breathable air mesh and synthetic upper materials. DynaMotion Fit upper moves seamlessly with the foot. INTERCOOL ventilation system reduces heat and humidity build-up inside the shoe during performance. Lace-up closure. Lightly padded tongue and collar. Soft collar and interior lining helps reduce the likelihood of irritation. Removable foam insole. Top midsole layer features U4ic compound for 33% more response and greater durability. U4icX strobel lastiThe Mizuno? Wave Rider 21 running shoe lets you embrace the rush of the road with its smooth construction and superior traction.Predecessor: Wave Rider 20.Support Type: Neutral to underpronation (supination).Cushioning: Lightweight, flexible response.