Resistance tubing connects upper arm with hand to encourage a correct bend in the elbow. During backward movement, tubing provides moderate tension to develop powerful back swing while it helps to accelerate the arm during forward propulsion. Sprint Trainer features a cuff that attaches around the upper arm and a loop that goes around the finger and thumb. Lined thumb grip keeps tubing from cutting into the hand. Velcro cuff fits up to 17" bicep. Green. 1 lb. Sold as pair.