Abstract: A die assembly is provided which is suitable for the extrusion coating of elongate cores, such as optical fibers. The die assembly comprises a nozzle having an orifice therethrough. A die tip has a through-bore and is mounted such that the through-bore is alignable with the orifice to conduct a core through the through-bore and orifice. A passage is arranged for conducting a flowable coating material into and through the orifice. A hollow guide tube is slidably mounted in the through-bore and is sized to receive the core. The guide tube is positionable such that the forward end thereof is movable relative to the nozzle orifice.