Also, what you REALLY need to watch out for... is you HAVE to line up the plastic trim piece the belt goes through just perfect into the little hole on the mechanism (the part that allows you to adjust the height it sits on the shoulder) or the belt wont retract at all. I figured that out the hard way when I took the trim off to remove my rear door panel. I thought the belt itself was messed up, and it was under warranty, so I took it to a dealer, they got me a new belt... but the only thing wrong was that I didnt align it back up right. Once you get the trim off, you will see what Im talking about. At least, this is how it is in my ZX3, not sure about the sedan/ZX5/wagon.
My car: 2014 Focus ST3
My Moms: 2009 Sangria SES Sedan
My Bro's: 04 Silver ZX5 SVT EAP
Team Duratec # 136