product 1. Large Stability Ball - The ultimate workout buddy, this 55cm yoga ball effectively works your arms, legs, back, chest and abdominal muscles - while effectively strengthening your core and helping improve your balance.2. Helps Improve Posture - This large yoga ball can also be used as a chair replacement on your desk to help relieve back pain and improve posture. By working your core muscles, you can strengthen your back, help tone your spine, and relieve stress on your upper body.3. Easy to Inflate - Its also easy to inflate the stability ball with the included hand pump - you can do the whole thing in 90 seconds or less When you need to add more air to the ball to get it back into firm shape, its easy to refill with just a hand pump.4. Pregnancy Helper - Pregnant women may also find this inflatable ball very beneficial, it helps them maintain a comfortable sitting position in the place of their choice. The ball can also be used to perform pregnancy exercises, strengthen leg and back muscles and help prepare for labor.