Synthetic-and-mesh fabric sole SHOE SIZE: "B" = Medium width THIS SHOE IS FOR: This is a great option for neutral, efficient runners who don’t like a super soft shoe. It has just-right spring and is light enough to be a race shoe for longer distances like the marathon. ENERGIZED FEEL: Delivers a responsive and springy ride to add extra lift to your stride without compromising support or speed. SPRINGY CUSHIONING: BioMoGo DNA midsole cushioning and rebounding rubber create a springy feel underfoot. LIGHTWEIGHT FIT: The one-piece mesh upper and internal bootie are so light and breezy, they feel like they’re not even there.