Will this connector work?

I'm almost done putting together my new rig, but I have a problem. My new graphics card (580gtx) requires a 6pin and a 8pin connection. I have only 1 8pin coming from my power supply, but that goes to the mother board.
What I do have is a wire that came with the Corsair 550w, it turns a 6pin into a 8pin.

Will this be ok to use as a 8pin?

Anyone know if its ok for me to use this 8pin connector when it comes orignally from a 6pin?

The picture you show is a little vague, as it only shows one end of the connector. It does look like one of those 6pin to 8 pin connectors. I take it that both the six pin female connector shown plus the two pin female connector shown both connect up to another six pin male connector that is not shown. If this is all true, then yes, you can use this, but it is a less than ideal way of doing things. Otherwise give the model of the PSU and I'll check more in to it.

However, what worries me is that you are pushing a GTX 580 on to a 550Watt PSU. please post all parts in this rig so we can find out what the power draw will be, I suspect your PSU is not big enough.

^^ 550w should be plenty(80+ & respected brand). However this is dependant on the rest of the OP's setup as well.

OP the manufacturers usally split connectors to allow for compatibility with a wider ampount of setups. That connector is a 6 or 8 pin connector.