What SLI connector do I need?

Westindieman

I am connecting 2 ASUS Geforce 670 GTX and thought the SLi connector would be supplied with the cards or the motherboard but it isn't.
I have googled the connectors but it seems there are different sizes 3'', 4.7'' for example. I don't know what I need to connect my cards and its difficult to get this information by googling. Can anyone help?

Thanks