Big Mike's Fitness Power Twister Effective upper body workout: great for building your hand, wrist, forearm, bicep, triceps and back muscles Heavy duty and durable : heavy duty high grade double spring & handle grip Portable and lightweight : great for travel, easy to carry and transport Multi workout tool : not only does it increase upper body strength, but also stabilizes core Designed for increasing strength and safety : harness the safety rope in the grip onto your wrist before using, so as to prevent hitting others