Puma Run XX Nitro Womens Black Running ShoesThe Puma Run XX Nitro is engineered with a progressive, female specific design, reflecting Pumas commitment to the "RUN FOR HER" motto. Named after the double X chromosome, this shoe features an updated fit that contours to a womans foot at the heel, instep, and arch. The firmer NITRO foam midsole offers a balance of durability and lightweight cushioning, while the RUNGUIDE system promotes proper alignment and increased stability for longer distances.