Arrow shaft length also must be matched to your bow. Drawing an arrow that’s too short is dangerous because it may slip off the bow, while an arrow that is too long weakens the spine of the arrow. Arrow tables can help you make the right selection.
Aluminum arrows are labeled by their outside diameter and the wall thickness of the shaft. A thicker shaft provides greater stiffness.
Aluminum and carbon-fiber combination arrows are measured by spine deflection. A smaller number means that the arrow has a stiffer spine. For example, 3-60/340 means three wraps of carbon-fiber with an aluminum core tube diameter of 60 and a spine stiffness rating of 340.
Carbon arrows also are labeled to indicate their spine deflection. The most common spine sizes range from 260 to 500. As with combination arrows, a smaller number means the arrow has a stiffer spine. Therefore, a value of 340 indicates a stiffer and heavier spine while a value of 500 indicates the lightest and most flexible spine.