Swiss balls are large, heavy-duty inflatable balls with a diameter of 45 to 75 cm (18 to 30 inches). The Swiss ball is also known by a number of different names, including exercise ball, gym ball, Pilate's ball, sports ball, fit or fitness ball, stability ball, therapy ball, yoga ball, balance ball, body ball, or birth ball. Swiss balls offer you a fun, safe and highly effective way to exercise. They will last for a very long time and are inexpensive compared to other exercise equipment.