in an extrusion head and an extrusion method for the production of a tubular multilayer preform the extrusion head includes at least two feed paths for feeding plasticised plastic material from one or more extruders to an annular passage arrangement . the annular passage arrangement includes mutually concentric annular passages forming mutually separate flow paths for the various layers of the preform . an annular gap nozzle has an annular gap communicating with the annular passage arrangement , and at least one flow passage communicates with an annular passage of the annular passage arrangement , for the introduction of a translucent viewing strip . the flow passage communicates with the annular passage in question upstream of the annular gap in the region of separation of the flow paths .