Zuanjia ZRX5 Varigrip Adjustable Hand Exerciser Improve Hand & Finger Strength, Endurance and Dexterity Develops and maintains the strength and dexterity of your fingers, hands and forearms, and it allows a larger number and variety of hand & finger exercises and ensures all hand sizes are catered for. Variable tension provides customized conditioning for individual fingers(3 to 8.5 lbs of tension) means you can adjust the level of difficulty to suit the strength of each finger. Zuanjia hand strengthener is uses soft malleable rubber for supreme comfort and quality copper core (not cheap steel) for maximum durability. Perfect tool for pre-show warm-ups and maintaining conditioning when away from your instrument,it can fits in your pocket so you can use it anytime and anywhere. The ultimate conditioning tool for all musicians, We back this product with a lifetime warranty.