A low 4 mm drop encourages natural foot position while bringing a brand-new running experience to the Altra line. This low drop complements the shoe’s rocker shape geometry for an efficient toe-off and a smooth, quick roll through your stride. Featuring the same roomy toe box you know and love so you can move as you were designed to, plus an all-new lightweight and responsive compression-molded midsole foam. With the Experience, you’ll enjoy an effortless run with the perfect blend of comfort, performance, and style. Upper - Engineered mesh.