Will this really work with r3?

Yeah..., NO!!!
I would be VERY leary of this one, as the picture shown is of an Akrapovic, and the product description is of a Yoshimura. Honestly, I'd keep shopping around and read product descriptions thoroughly to be sure you're not getting shafted by some aftermarket knock-off.
To my knowledge, the R25 and R3 pipes are compatible though.

Haha good eyes. I totally missed yoshimura in the description.

I got screwed on eBay once. Won't happen again. You can buy a really nice Akrapovic slip-on from Chaos Theory Racing (jbluetooth on our forum) for less than that too.