Side Feed Fuel Injector Top Metal Pin

[kpjo4]

I was just curious as to what is the purpose of the metal pin on nissan side feed injectors? I'm asking because not all side feed injectors use this, pin. Is it there for a mounting guide for the fuel injector top cap with that rubber grommet piece? Or does it depress to open some sort of valve? I'm just curious and have been on Google search and multiple forums but I cannot find any information.

http://www.fiveomotorsport.com/catalogues/198/infinityq45new_600.jpg