The reebok mens training 75cm two tone gym ball is a highly versatile piece of fitness apparatus designed to increase core strength and work on posture balance flexibility and general fitness the two tone stability ball has a double coated rubber base that delivers more stability to keep you balanced when exercising and it is great for performing efficient drills such as crunches the plank tricep dips shoulder curls squats and more switch on the workout dvd that comes with the swiss ba