The GripMaster hand exerciser has been used by the U.S. Military and Federal Law Enforcement to improve shooting accuracy. When using the device, each finger individually conditions its own muscles and tendons by exercising with its own spring, resulting in increased hand, wrist, and forearm strength. GripMaster comes in three color-coded models of increasing resistance: Blue is recommended for the average woman’s hands, red for the average man’s, and black for only very strong hands.