Grip Strength Training, 3-inch Hardwood Pull-Up Cannonballs - Ninja Warrior Climbing Holds & Crossfit Training, Set of 2 EXTREME GRIP STRENGTH TRAINING - 3-inch solid hardwood balls for training rock-climbing grip strength, American Ninja Warrior training, Parkour, Crossfit, obstacle racing, Grappling and more. WEATHERPROOF TEXTURED COMFORT GRIP - Light texture allows for no-slip grip but will not hurt your hands. Weather sealed for durability and outdoor use. EASY TO USE by simply hanging from nylon webbing, quick draws, chain or rope. COMPATIBLE with Slackers Ninja Line for American Ninja Warrior, rock climbing and Crossfit training 100% Manufactured in the USA. Load tested to over 1,000 lbs! Please be sure to hang them from something that will adequately support your weight.