Solid Base: 

Double triangle stable base, safe upgrade, reduce creep down when standing upside down. 

Back Waist Cushion:

Waist cushion fits lumbar vertebra better, can be changed to air inflated cushion.

Fixed Foot Device: 

U-shaped PU fixed foot device, fits your ankle better and more safe.

Automatic Foot Presser:

Double safety automatic foot press device, make sports safer and more comfortable.