a polymer extrusion head for forming continuous shapes having one or more lumens therein . the head includes an extrusion mandrel and die . at least one lumen pipe is disposed radially through a port in the die to intersect the polymer flow in the annular region between the tip and the die . the lumen pipe is a welded assembly having a 90 ° turn formed as a mitered joint with zero bend radius . the lumen pipe is held in a pin vise engaged in the die such that position of the lumen pipe may be readily adjusted . axial and radial positions are established during assembly by means of a gauge block . a plurality of lumen pipes may be accommodated for a plurality of lumens by a manifold distribution system including individual lumen pipe assemblies .