The news release from General Motors regarding the GMC version of the truck talks about the same with regards to the Fifth-Wheel/Gooseneck provision package, what it contains; and what the significance of equipping the truck with this package is.

Meet the 2016 GMC Sierra 2500HD heavy-duty pickup truck with unequaled versatility and capability.

Source: 2016 Sierra 2500HD: Heavy-Duty Pickup Truck – GMC