Pilates balls, also known as stability balls or exercise balls, are large, inflatable spheres used in fitness routines. They come in various sizes, typically ranging from 55 to 85 centimeters in diameter, and are designed to improve balance, flexibility, and core strength. These balls are often used in Pilates workouts, but they can also enhance other forms of exercise, such as yoga and strength training. By incorporating a Pilates ball into workouts, users can engage their muscles more effectively and challenge their stability, leading to improved overall fitness.