The Suspension Mobile Arm Support is designed to allow you to comfortably and safely support your arm. When in use the rotation occurs behind, or next to the side of your arm at your ball bearing joint, to be closer to center of gravity. The addition of our new Forearm Support Slide allows your forearm to be balanced quickly and easily with minimal tools required. Sizing should be measured by the distance from Olecranon Process to Ulnar Styloid minus 1-1/2". If the measured distance is 1/2" longer, choose next larger size.