Grip Trainer is a finger-hand-forearm exerciser and is ideal for anyone participating in sport, hobby or pastime that needs strong hands and forearms. Features 3 LEVELS OF DIFFICULTY Green 30lb max resistance (easier) Black 40lb max resistance (medium) Red 50lb max resistance (most difficult) Description Grip Pro Trainer eliminates the uneven workout of spring exercisers, is far more dynamic than grip balls and not difficult like gyros. USE IT ALMOST ANYTIME/ANYWHERE…desk, car, walking etc. Grip Trainer has a natural feeling in the hand, yet is dynamic to use and very effective. When routinely used in 3 sets of 30 to 100 reps it noticeably improves finger-hand-forearm strength.