JumpNRope Speed Balls Jump Rope Symmetry and Strength Trainer THE SECRET WEAPON - This powerful training tool will automatically expose and correct lapses in turning symmetry, strength and hand position. Master the speed balls and you'll quickly master your double unders! DESIGNED FOR AND BY WORLD CHAMPIONS - Speed balls were designed by 5-time world jump rope champion Molly Metz as a tool for her own competitive training. How do you suppose she developed the stamina for 1,400 consecutive double unders without a miss? WE OWN THE PATENT - The technology behind this uniquely patented handle is owned by JumpNrope. WE INVENTED IT. You won't find a faster, smoother, higher performing jump rope system anywhere. Yes there are imitators, but don't be fooled - This is THE ORIGINAL...designed, built and sold to you from the source. SIMPLE, DURABLE, LASTING - Highest quality glass-filled nylon handles, multi-stranded stainless steel cable, thick PVC coating, dual stainless steel precision bearings. Meticulously hand made in Colorado with high quality U.S. materials. This product stands up to the high demands of amateur and professional athletes alike. WE STAND BEHIND OUR PRODUCTS - At JumpNrope, customer experience is at the core of everything we do. If youre not completely satisfied, tell us. Well do everything we can to fix whats wrong and win back your business and your respect.