⭐ One size fits all (up to shoe size 13). ⭐ Strong and lightweight design. ⭐ Anti-Slip Surface, curved stretching tool. ⭐ Double Protective Rubber Stripes ⭐ Fully Portable, stripes and grooves increase the friction for safe use. ⭐ Design automatically holds the foot in the optimal position for proper stretching, providing a bio mechanically accurate & efficient stretch that's been proven to work the lower leg muscles more effectively than conventional methods.