Whether you're training for a marathon or just enjoying a casual run, the Nike Air Zoom Pegasus 41 is the ideal all-round running shoe. Take on your running challenge with the Air Zoom Pegasus 41. Midsole The midsole of this shoe is made of ReactX foam. ReactX is a lightweight, firm foam that delivers a smooth, responsive ride with significantly reduced impact. With 13% more energy return and 43% fewer carbon emissions than regular React foam. A Zoom Air unit built into the midsole of this shoe absorbs impact and then bounces back quickly, reducing stress on muscles, joints and tendons. Zoom Air units allow you to run faster and jump higher because they transfer energy more efficiently. Upper Air Zoom Pegasus 41's mesh upper keeps the shoe breathable and comfortable while running. Outsole The rubber outsole provides the shoe with good grip and traction while running. The outsole also has flex grooves to create more flexibility in the forefoot. This shoe has Nike's characteristic waffle pattern as an outsole, with short rubber studs in the shape of honeycombs, for grip on wet and dry surfaces.