Ball Set. Combines three of the world's most popular ball sports. Diameter: 11 cm. Material: Rubber. Great training for coordination and learning throwing and catching techniques. They also provide great fun in the water. The hardness of the ball can be adjusted by pumping it up. One product, three balls, full action. The Schildkröt 3 in 1 Mini Ball Set combines soccer, football, and basketball. They are excellent training for coordination. The three small balls are lightweight and soft (Ø 11 cm, approx. 50 g) and are suitable for all age groups. They also offer great fun in the water. The hardness of the ball can be adjusted by pumping it up (max. air pressure 0.17 bar).