Enhances core muscle strength and development by isolating specific muscle groups * Can be used standing, sitting, kneeling, lying down, and in tandem with exercise equipment such as balls or resistance cables * Made of soft, pliable PVC with a nibbed surface on one side * 13 inches in diameter and 3 inches in height * Anti-burst, can withstand 500 pounds of pressure, and can be re-inflated using standard bicycle pump and pump adapter