the type marketed by buler ag of 9240 uzwil switzerland via said extruder 39 s outlet flange 30 it is similarly connected to a multi channel cooling die 50 whose extrudate flow channels 40 are arranged radially about a circular axis for example as disclosed in patent document no wo 01 49474 via said cooling die 39 s inlet flange 35 this attachment is partially indicated in fig3 wherein the position of the extrudate flow channels 40 is also indicated the cross sectional view shown in fig4 shows the structure of the device 5 and its essential operational features in particular it 39 s internal geometry the device 5 is shown attached to a twin screw extruder having compression screws 38 of approximate diameter d and to a multi channel cooling die 50 the positions of the extrudate flow channels 40 are shown in particular it will be noted that the length of the typical extrudate flow path l relative to the diameter d is greater than about 1 7 1 those skilled in the art and in particular those persons familiar with the flow of extrudate fluids will perceive that the relative length of this flow path will greatly assist in the promotion of laminar flow of the extrudate 42 through the device 5 and on into the channels 40 the device 5 is characterised by three main zones a flow restricting zone 55 of decreasing overall internal diameter in the direction of flow and which also gradually transforms the internal profile of the device 5 from an ovular shape matching the extruder outlet to a substantially circular shape a throat 60 of substantially circular profile at which the minimum overall internal diameter is reached and an expansion.