Gripmaster Pro Hand Exerciser - 2 Pack-Gray. High-quality hand exerciser with spring-loaded finger piston technology. Isolates and strengthens each finger individually for better overall coordination. Improves user control of bats, racquets, clubs, guitars, and other sports equipment. Fits conveniently in your pocket; lets you strengthen fingers anytime, anywhere. Heavy tension strength of 9 pounds per finger for strong hands.