That one appears to be missing the base to the camera Boo, plus they've got the reflectors marked as a track clip (which has independent lights on 3 arms).
Personally, I'd buy one from Naturalpoint - I'm always wary of buying anything 2nd hand/used etc (that could just be me though).
That will work with the version 5 software just for info.
Should you buy trackir for this game - imo, yes, but again, thats just me.
Wurz