By opening and closing your wrists while gripping, you are essentially using both your forearm flexors and extensors. Increasing the strength and size of your hand muscles will make your arms appear more powerful.

Principal Advantages:

It has 10 to 40 kg of programmable resistance settings. crafted from premium materials for enduring use. 
ergonomic non-slip grip for ease of use.
 Boost Hand Endurance and Strength
aids in hand rotation exercises and motion exercises.
 a useful stimulant when taken often.
 It is a tried-and-true, incredibly successful hand therapy. 
specifically created to meet patients' do-it-yourself needs.
 NOTE: Depending on the availability of the stock, the hand gripper's color may change.