The Gym Ball - 85 cm is a fitness tool designed for core strengthening, balance, and flexibility exercises. Its larger size suits taller individuals, providing stability during workouts like crunches, squats, and stretches. Using it engages core muscles and enhances balance by introducing instability. It can also replace a traditional desk chair to promote active sitting and better posture, reducing the risk of back pain. Overall, it's an effective tool for improving fitness and well-being at home or in the office.