Abstract: Apparatus (10) for manufacturing polymeric tubing (T) containing a reinforcing material (M) enclosed between first and second polymeric compounds including an extrusion head (11) having an elongate housing (14), a bore extending from a front end (15) of the housing to a rear end (16) of the housing, a rear material guide sleeve (50) fixed in the bore proximate the rear end of the housing and having a channel (51) for passing reinforcing material, a forward material guide sleeve (36) fixed in the bore proximate the front end of the housing for radially outwardly constraining passing reinforcing material, a center pin (76) extending substantially the length of the housing and located centrally of the bore thereof, a flow pipe (60) extending from the rear material guide sleeve and forming an inner channel (90) supplying a first polymeric compound, means for adjusting the concentricity of the flow pipe relative to said center pin means, an outer channel (45) supplying a second polymeric compound, and adjustable d