It is the GMC Wheel Lug and Wheel Stud that the tires and wheels are mounted too so they can be attached to the rest of the vehicle. These small but very significant components are essential for the transfer of motion so the GMC truck can literally roll down the highway.
The GMC wheel studs are like no other bolt on your vehicle. They have threads at one end, but the other is just a blunt surface with a rim and striations on it. This makes it possible for the studs to be placed in the wheel hub and remain there without moving as the wheel lug nuts are tightened up in them. There are at least 5 studs and lugs for each wheel on a GMC truck. As the gross weight of the truck increases, so does the number of studs and lugs holding the wheel firmly in place.
The wheel lug nuts are also different than all other nuts on your truck just like the studs. They have one side that is flat like all other nuts, but the other side of the nut is beveled. This makes it possible for the lug to fit into the opening of the wheel slightly. This locking mechanism uses the wheel as a kind of lock washer so it will not become lose when the GMC truck is in motion.
The combination in the uses for the wheel studs and lugs are designed for the specific purpose of keeping your wheels in place while they are in motion. The torque required for keeping them in place is more than most other bolts and nuts have put in place with. This is why they are larger than most others on your truck.