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. ROLLBAR stability post system helps control rear-foot movement for enhanced support Lightweight solid rubber outsole 4 mm drop; due to variances created during the development and manufacturing processes, all references to 4 mm drop are approximate Adjustable lace closure for a secure fit