Byrd Bands™ are a simple innovative method to encourage proper arm position for runners.Fully adjustable for all size athletes. One aspect of proper running form related to sports is that the angle between the lower arm and the upper arm is maintained at approximately 90º. For some athletes it can be difficult to maintain the 90º arm form because often times they have been taught incorrectly or appropriate focus to this aspect for form has been overlooked.Sold in sets of two (2).