NIKE Men's Air Relentless 4 Running Shoes Synthetic UPPER: Great lightweight pattern with a midfoot TPU panel for lockdown. MIDSOLE: Phylite midsole for a lightweight ride and air unit in the heel offer the right blend of cushioning and a smooth ride. OUTSOLE: BRS 1000 in the crash pad for durability. Solid rubber Waffle pattern in the forefoot for great traction. A blend of lightweight and structure which provide a supportive minimalistic shoe.