Train like a warrior! Our Ninja Balls are one of the top training devices for building forearms and grip strength on the Ninjaline hanging backyard obstacle course. Switch up your course with the hanging strap which allows for full shoulder rotation. Plus, the smaller size is perfect for more advanced users to challenge themselves! Perfect for use on our Ninjaline™ (sold separately). Endorsed by Brian Arnold “The Ninja”, Brian Arnold is a recognized expert in ninja warrior competition and training as a highly successful warrior. He is the ninja that beginner warriors turn to for training tips. In his free time he likes to rock climb and train with Slackers™ slacklines and Ninjaline™