D'Addario Accessories, part of the D'Addario family of brands, is known for innovative, problem-solving, quality musical accessories. The Varigrip Hand Exerciser builds and conditions the strength and dexterity in your hands, wrist and forearms while increasing hand speed and endurance. The reversible moulded grip even uncovers simulated strings to help develop and maintain finger calluses when you are away from your instrument.