I'll give you my opinion. Unless you plan on racing your X, it's all just for show. Based on your lack of information in your post, one can only guess that you intend to replace rotors on a 4.6. If that's the case, you are throwing money away. The OEM rotors for a 4.6/4.8 are insanely huge and will stop these big SUV repeatedly with no fade. Save the money for airbags and suspension bushings.

__________________
2006 4.8iS Black/Black with custom Audison Voce/Image Dynamics sound
Production Date - 10/05