Fresh Foam X midsole foam with approximately 3% bio-based content delivers our most cushioned Fresh Foam experience for incredible comfort. Bio-based content is made from renewable resources to help reduce our carbon footprint NDurance rubber outsole technology provides superior durability in high-wear areas to help get more out of these running shoes Engineered air mesh upper Reflective accents designed to catch the light 6 mm drop; due to variances created during the development and manufacturing processes, all references to 6 mm drop are approximate