Reebok RunTone Vibe U-Form Womens Running Shoes Synthetic RunTone is designed to improve your workout and run allowing you to get the best rewards by toning and strengthening key leg muscles Lightweight and breathable mesh upper with synthetic overlays for support SmoothFit upper ensures a comfortable and irritation-free fit U-Form custom fit technology uses heat activated materials to mold to your foot for the perfect fit 8 balance pods built in on the sole creates natural instability in every step to force your muscles to adapt and encourage toning