Milliard Anti-Burst Peanut Ball Variety Pack - Approximate Sizes: Green 39x20 (100x50cm) & Blue 31x15 (80x40cm) Physio Roll Used to improve posture and in weight lifting exercises to increase core strength Easy to integrate into almost any training regimen. Great for use at the gym, in yoga, or in your living room. Used to promote labor progress specifically in epidural birth To inflate the peanut ball to its full size, pump the ball with included hand pump. Add more air after 12 hours until it is fully expanded. Anti-burst rubber compound prevents the ball from violently bursting if punctured. <span class="a-text-bold">WHICH SIZE BALL IS RIGHT FOR MY CHILD?</span> Measure from the tip of your childs fingers to his armpit. Chose a ball sized within 2-6&#034; of the measured length for a comfortable fit. <span class="a-text-bold">WHICH SIZE BALL IS RIGHT FOR MY DOG?</span>The ball should be approximately the same length as your dog from head to tail. For extra large or extra small toy breeds use the largest or smallest peanut respectively.