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.degree. 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.