Geospace Jumparoo JACK HAMMER Extreme Pogo Jumper by Air Kicks Uses a totally unique bow-shaped spring to propel riders to heights of up to 4 feet! Available it 2 sizes, Small or Large, suitable for Ages 13 & up. Small is for users weighing 120 to 154 lbs (54-70 kg). Large size is for users weighing 154 to 176 lbs (70-80 kg). Composite fiber spring and high-grade aluminum body means JackHammer weighs only 8 pounds!