2006 GMC Sierra 4x4, model 2006, 6-stud. I bought it thinking it would fit an 8-stud axle, but it didn't. Now I'm selling the 4x4 system and its axles. (((((Contact via WhatsApp))))) The brown color on the 4x4 system is not rust, it's dirt and oil. (Phone number appears when you press the contact button)