Version: Basic. The Powerball hand trainer – for individual and effective hand training. The Powerball is a gyroscopic hand trainer. It operates entirely without batteries based on the principle of gyroscopic force: The rotation ball is set in motion purely by muscle power. This has the significant advantage that the rotation ball always adapts to your training level. As an advanced user, you can reach up to 16,000 revolutions per minute. Depending on how you hold the hand trainer, you can strengthen different muscle groups. More comfort with the Powerball AutoStart. The Powerball AutoStart is additionally equipped with a rotor, allowing for easy starting without a cord. Especially beginners no longer need to practice the start laboriously. Product details: Weight: approx. 250 g, Material: plastic, rubber edge, Diameter approx. 7.5 cm. Product type: wrist trainer.