CONNECT TO YOUR RUN. Top to bottom, Nike Flex RN 2018 Men's Running Shoe is built to flex. Its circular-knit upper stretches in key areas, while the dynamic heel design and molded Tri-Star outsole pattern work together for an adaptive ride that connects you to your run. ﾕ Circular-knit upper provides strategic stretch and support. ﾕ Dynamic Flywire cables deliver a locked-down fit. ﾕ Tri-Star outsole pattern enhances flexibility. ﾕ Minimal heel design is made with soft foam to secure the back of your foot while allowing natural movement. ﾕ Co-molded midsole uses a softer injected unit (IU) core foam directly underfoot and a slightly firmer injected unit (IU) carrier foam to deliver softness and support just where you need it.