Geomet Sports Hand Grip Strengthener with Adjustable Handle Resistance Ergonomic and lightweight design. For all hand sizes. Adjustable tension levels. No need to buy more than one hand strengthener! Made with the highest quality materials: stainless steel spring resistance system and compact molded rubber. Musicians and athletes can use the hand strengthener to increase hand, wrist, forearm, and finger strength and improve small muscle performance. This hand strengthener passed hand testing and rigorous quality assessments for safety and overall construction.