TheraBand Stability Disc is 33cm (13") in diameter. 

The disc offers an unstable, sensory-stimulating surface designed to facilitate balance and proprioceptive training, as well as automatic postural reactions. 

Portable and convenient.  Work on your balance for your core, shoulders and legs.

The disc is already inflated for your use. The inflation level takes your foot slightly off the ground to provide slight instability.

It's also ideal for active sitting.

Exercise Instructions included..