The 77663 Fiber Bundle Ferrule is an aluminum cylinder that attaches to the tips of fiber bundles, using set screws. Fiber ferrules can adapt your own fiber bundles, or replace lost ferrules. This 11 mm fiber ferrule has a 0.16 inch inner diameter and 0.48 inch length. 11 mm fiber ferrules give all our bundles a common external diameter of 11 mm (0.44 inch). This allows the same holders and positioners to be used for all bundles simplifying coupling and positioning.