50Pcs Pack of bobbin insulator The tension bobbin insulator large plus is used with both square, rectangular and Round posts as a pull through system for corners and change of direction. The tension bobbin insulator in conjunction with the pull through hook can be used to guide the wire around corners and bends. The round tension insulator guides the wire around the corner and holds it in place. Specifications UV stabilized for external use. Only virgin materials are used in their manufacture.