To clarify, in this instance, a “shoulder” is a large indented surface. For Double Shoulder Technology, the first shoulder is designed to address the issue commonly found in other inserts—not enough adhesive space. Small adhesive surfaces can cause an insert to easily dislodge itself from an arrow and consequently force the insert and arrow tip to move rearward and mushroom. Beside the first shoulder, the second shoulder (hence “double shoulder”) is designed to perfectly mate with a smaller ID carbon shaft (i.e. Carbon Inner Tubes) to form the AeroConcept System. Further, with a Carbon Inner Tube, your adhesive surface increases exponentially.