There is two types of lug bolts. My car is in transit and have been trying to get some help from the forum to see which type the xf has. Here is the site that has the different ones:

http://wheelaccessory.com/lugbolts.html

The rims I got off of a 05 slk take the ball, but don't know if the xf has the same. If you find out let me know please.