What is disclosed is an adjustable wide-slit extrusion nozzle containing a distributor channel having a straight exit edge and a cross-section taken from the supply port for the nozzle to one end thereof which corresponds to the equation:R.sub.i =R.sub.o (b/B).sup.1/3,wherein:B is the width of the distributor channel from the supply port to one end of the channel;b is a width coordinate measured from one end of the distributor channel;R.sub.o is the hydraulic radius of the distributor channel at the supply port; andR.sub.i is the hydraulic radius of the distributor channel at the distance b from the channel end.At least one choker bar insert is placed between the distributor channel and the nozzle mouth; the choker bar has a damming area surface whose length dimensions L.sub.i in the direction of flow at distances b from the channel end correspond to the equationL.sub.i =L.sub.o (b/B ).sup.2/3,whereinL.sub.o is the length of the damming strip at the supply port;L.sub.i is the length in flow direction of the damming area at the selected distance b from the channel end; andb and B are defined as above.The damming area rises above the remaining surface area of the insert, before or behind the damming area surface, in a uniform jump H, of from 0.1 to 5 times the exit height H.sub.3 of the nozzle and is a height-adjustable parallel faced mounted in the nozzle.