to form a downwardly extending parison a hydraulic cylinder 36 has a piston rod 38 connected to the piston 34 for moving the piston 34 downwardly operation of the accumulator head thus described is as decribed in u s pat no 4 609 340 located around the lower end of the die mandrel 20 is a ring shaped die ring 40 having four equally spaced guide portions 42 44 46 and 48 these guide portions are diamond shaped in vertical cross section as shown in fig4 to smoothly split the flow of melt as the melt is pushed by piston 34 past guide portions 42 44 46 and 48 a second conventional extruder 50 is connected to die ring 40 by a second inlet body member 52 the second extruder 50 provides an intermittent flow of a second extruded thermoplastic melt material 54 preferably a transparent material to extrusion head 10 through a second inlet passage 56 in second inlet body member 52 and a passage 58 in die ring 40 passage 58 extends through die ring 40 and through the underside of guide portion 48 passage 58 opens to the inside of the die ring 40 and the underside of guide portion 48 as shown in fig3 and 4 the injection of the second melt material 54 via second extruder 50 is timed to coincide with the passage of first plastic melt 16 by mandrel 20 and out annular outlet orifice 32 to form a tubular parison having a vertical strip of second melt material 54 which then is blown to form the storage drum.