The reebok womens training 55cm stability gym ball has a weighted base that grips the ground and stops it rolling away during use keeping you stable and safer when exercising this two tone anti burst swiss ball is a great choice for performing sit ups and many other exercises that focus on core strength stability balance and general fitness the exercise ball is 55cm 216 in diameter and suitable for users between 155cm and 167cm 5ft 1 and 5ft 57 tall the fitness ball is made u