I'm pretty sure kine was meant to have two bays, but when I opened it up it's only one. My original plan was ssd + normal drive :-(
Didn't you buy a PCSpecialist laptop?
If so the second bay is a replacement for the dvd drive so if you have one of those you'll have to order the hd bay.
That's what i did. I have an external dvd drive, which i've never used, and got a second drive in the bay.