Eduello :
ImperialistMillitant :
They come with the motherboard as far as I am aware.
They should come with the GPUs whereas SLI bridges come with the motherboard. What GPUs are we talking about? Are you sure they are crossfire compatible? Also, please remember that the most powerful AMD cards like the R9 290 and 290X don't need a crossfire bridge.
He is using an R7 260x which is in his Signature thingy.
Only the R9 290/x will run crossfire over the PCI. Generally low end cards don't come with crossfire bridges.
Personally its not worth crossfiring the cards. I would just purchase a medium/high end card outright.