ring 22 fixed to nozzle 12 and the end of housing sleeve 16 b ejector sleeve 18 is also spring biased to the released position of fig1 a by a compression spring 24 extending between an interior shoulder 26 of sleeve 18 and a shoulder 28 on inner housing sleeve 16 b in order for nozzle 12 to be movable as discussed herein a flexible connection for example a flexible hose should be provided connecting the nozzle to its drive piston or other drive mechanism for aspiration and dispensing a latch mechanism 30 is provided which includes a button 32 mounted in outer sleeve 16 a of the housing button 32 is biased toward the latched position shown in fig1 b by compression spring 34 mounted inside collar 36 extending from housing sleeve 16 a spring 34 extending between an outside wall of housing sleeve 16 a and an inside wall of button 32 button 32 has an enlarged generally circular inner end 38 and a narrower shaft portion 40 connecting the large end 38 to the remainder of the button 32 sleeve 18 has a keyhole slot formed on the side thereof adjacent button 32 the slot having an enlarged forward portion 42 which is slightly larger than enlarged tip 38 of button 32 and a narrower rear portion 44 fig1 b which is slightly larger than shaft portion 40 of the latch button but significantly smaller than enlarged portion 38 in operation the nozzle assembly 14 is initially in the released position shown in fig1.