The only major change was between the 2013 and 2014 model years with the OEM spring perch on the stock struts. However, since this package replaces both the front struts and the springs, you don't have an issue. That being said, Bilstein has not officially confirmed fitment on the 2018 Focus STs as of yet, though we expect a fitment confirmation soon. Installation is fairly straightforward, though it can be a bit of a bear to get the front struts out of the hub, due to how they're "clamped" in. You can check out our H&R Spring Install Video for an idea.