TwistyBAR 4-in-1 Interchangeable Weight Flex Resistance Bar, Comes with Bonus Free Ebook, Improves Tennis Elbow, Grip Strength and More The simple and easy exercises performed with TwistyBAR have been proven through scientific research to significantly improve Tennis Elbow, Grip Strength, and many more concerns including: hand, wrist, forearm, golfer&#39;s elbow, upper arm, and shoulder problems. Every TwistyBAR comes with 1 yellow core (5 lbs), 1 green core (10lbs), and 1 blue core (15 lbs) to perfectly suit everyone's resistance needs and abilities. Physical Therapists and Doctors LOVE the TwistyBAR and the fast results their patients achieve from working with it. Portable, convenient, and easy to travel with. Take the TwistyBAR with you to work, on trips, or anywhere else. TwistyBAR&#39;s ease of use and ability to interchange weight in seconds allows you to focus on achieving your fitness and wellness goals.