74 is mounted on the valve member 50 and this is then inserted through the first nozzle part 22 and the spring 72 the collar 14 is then placed around the first nozzle part 22 the collar 14 may be the collar provided with a container 10 or it may be a special collar 14 provided with the nozzle assembly 20 of the present invention with the collar 14 in place the second nozzle part 26 is inserted over the valve member 50 the tapered ends 71 engage the bore of the cylindrical portion 32 and resiliently press the arms 64 inwards when the second nozzle part 26 is fully engaged as shown in fig3 the arms 64 spring outwards so that the second catch surfaces 68 engage the first catch surface 36 it should be noted that it is essential for the second catch surfaces 68 to engage the first catch surfaces 36 remote from the disengagement cams 38 to ensure proper engagement this is readily achieved by simply looking in the direction of arrow 5 of fig3 as fig3 also clearly shows when fully engaged the abutment surfaces 70 engage the shoulder 80 formed between the cylindrical portions of the second nozzle part 26 the valve member 50 is thus secured to the second nozzle part 26 during the insertion process the compression spring 72 is compressed so that it is urging the first and second nozzle parts 22 26 apart as a consequence the sealing member 74 is clamped between.