quick question about wiring up a cool tube

I am planning on making my own cooltube, but the socket and cord I have looks like this :

I want to use one of these so the big socket doesnt block the air flow :



Its only 2 wires coming from the socket, but the end of my cord has 3 prongs on it. whats the extra wire, and what do i do with it ?

Or can I just remove the big hocky puck type mount from my standard cord/socket set ?

 

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