Nike Flex Runner 2 Boys Slip-On Sneaker Get him up and running in no time with the Flex Runner 2 boys Slip-On Sneaker from Nike. With a breathable mesh & synthetic upper featuring a heel strap for stability, this stretchy Shoe slips on easily with a reinforced toe to protect from dragging. The foam midsole cradles your foot comfortably, while the flexible outsole has deep grooves that offer multi-surface traction. Mesh/synthetic upper Slip-On Reinforced toe Foam midsole Traction outsole.