A quick tutorial on bend radius from the Fiber Optic Association: All FO cables have specs that must not be exceeded during install to prevent irreparable damage to the cable: pulling tension, min bend radius, crush loads. Installers must understand these specs & know how to pull cables without damaging them. Why is it important? Not following bend radius guidelines can lead to cable damage. If the cable is damaged in installation, the manufacturer’s warranty is voided. That means if you are pulling a cable over a pulley, that pulley should have a min radius of 260mm/10" or a diameter of 520mm/20" – don’t get radius and diameter mixed up!