Stylish and propulsive, you will be excited to lace up the Karhu Fusion 4.0. Get ready for quick, cushioned runs, this shoe is streamlined to work whether you are running long distance or kicking it up a notch with some tempo work. Our testers loved the smooth and snappy feel of their runs in our Karhu Fusion 4.0 review. Plus, with its new knit upper, it looks great for casual wear as well. Details: Upper: The stylish Ideal Knit upper feels as good as it looks with a snug, streamlined fit. Featuring Karhu’s signature M-lock midfoot fit, you will feel secure as you rock your runs.Midsole: The nitrogen-infused AeroFoam cushioning is responsive and snappy and when combined with Karhu’s Fulcrum technology, creates a swift and efficient underfoot feel.