The Nike Free TR 9 Ultra is lightweight and flexible to be quick and adaptable for whatever workout you take on. The slip-on design has Flywire cables to securely hold your foot. Soft, flexible foam cushioning has a wider surface area for more stability. FREE TO FLEX. FIT TO TRAIN. > Nike free sole is made of soft foam that's flexible to bend in any direction. > Heel is flatter to create a wider surface for more stability during exercises such as squats. > Synthetic material and fabric are durable and lightweight. > Flywire cables create a secure fit around your foot. > Slip-on design is easy to take on and off.