Description Build strength, balance & coordination: Joinfit soft & mini medicine ball or  toning balls are perfect for balance, flexibility & strength workouts. Performing exercises with an unstable ball engages your body’s deepest stabilizing muscles for coordination & maximized strength Pvc shell – unstable iron sand inside: Made of PVC and filled with natural Sand, our toning balls are durable to function well for a Lifetime. Natural Sand inside creates instability to activate different muscle groups for a leaner & tighter body Compact and portable for travel: you can definitely bring the balls along When you travel to have a mini workout. Also, you can keep them at the office and take them out to stretch or warm up your muscles during break or after a long day at desk Air pump available to adjust the floppyness.