Size choice: 33/35 M for 30kg-50kg body weight(66lbs-110lbs); Foot length:21.5cm-22.5cm 36/38 L for 50kg-70kg body weight(110lbs-154lbs); Foot length:23cm-24cm 39/41 XL for 70kg-90kg body weight(154lbs-198lbs); Foot length:24.5cm-25.5cm 42/44 XXL for 90kg-110kg body weight(198lbs-243lbs); Foot length:26cm-27cm Mesh+Pu Synthetic Leather Shell: TPU Spring: TPE Color: Black Relieve the shock and vibration with A shock-Absorbing Device(Flexible Spring) Easy to use with shoes on, suitable for your weight and the lenght of foot More calories and better fitness can burn by this way. it's easy to burn calories, build fitness, coordination and strengthen leg muscles. Please note ONLY XXL has THREE BUCKLES Notes: 1. Due to the different display and lighting effects, the actual color of the product may be slightly different from the color shown in the picture. 2. Due to manual measurement, please allow a measurement deviation of 1-3cm.