33 cm Stability Disc is ideal for developing balance and stabilization. The disk is 33 cm (13") in diameter and perfect for pushups, standing, kneeling and sitting exercises. It can be inflated or deflated to change the level of difficulty. its lightweight and portable so it can be used at home, at the office, or on the road. The disk has two sides; flat and textured. The textured side provides a non-slip surface. The texture also adds great sensory input which is soothing and comfortable.