Our Cortex 55cm fitness balls are extremely versatile and inexpensive exercise tools that can be used to work out nearly every muscle group in the body. They can be used to improve your posture, core strength and overall balance and stability. Lifespan Fitness balls are made of quality anti-burst, UV resistant material and are guaranteed to last. Fitness balls are extremely versatile and inexpensive exercise tools that can be used to work out nearly every muscle group in the body. They can be used to improve your posture, core strength and overall balance and stability. Lifespan Fitness balls are made of quality anti-burst, UV resistant material and are guaranteed to last. MATERIAL - Super Strong Anti-burst material - UV Resistant Material DIMENSIONS AND WEIGHT - User Weight: 300kg - Colour: Dark Grey - Size: 55cm