Merrelll Sprint Lace AC+ Shoe Adult Retro feels right in these trainers. The "M" on the outside's been there forever. The inside's evolved with responsive Aire Cushion+ for heel-to-toe support. Upper: Synthetic Microfiber Lining: Breathable Mesh Midsole: EVA with Air Cushion+ from heel to toe Outsole: M:Select Grip Rubber