The invention comprises a transmission line hanger insert that acts as an adapter that allows standard transmission line adapters previously used for coaxial cables to be used for fiber optic cables, power cables, hybrid cables and other cables that are becoming the new standard in the telecommunications industry. The insert is manufactured from UV-resistant rubber that is softer than the rubber used in prior art inserts.The insert of the present invention comprises a hollow cylindricalThe present invention is a hollow, spool-shaped cylindrical insert for a standard transmission line hanger that comprises a cylinder with a rim at either end, a round opening through the cylinder's center, a slit extending from the exterior of the insert to the interior opening and multiple standing ribs in the interior of the insert that allow the insert to be used with a plurality of different cable diameters and shapes.