The pin box/king pin assembly is the attachment point between the fifth wheel trailer and the towing vehicle.Should a complete fracturer occur in service, the trailer could become detached from the towing vehicle.In 1997, Fleetwood replaced the 7 gage steel used to construct the pin box with 11 gage steel, which is about 30 percent thinner.In mid 1998, Fleetwood went back to the thicker steel and has provided dealers with drawings and specifications to repair vehicles in the field with the thicker steel pin box.