The 65cm Stability Exercise Ball strengthens and tones the abs, core, and back and supports balance, flexibility, and recovery work across a commercial floor. Use it for Swiss-ball crunches, planks, push-ups, squats, and lunges, or for posture and physical-therapy programming. This 65cm size suits users between 5'5" and 5'11"; size down to the 55cm ball for shorter athletes.