Welcome miker!
The exterior length is measured from the center of the kingpin to the rear, including the bumper
(or bumper 'area' if shaped/molded vs tubular bumper).
The length listed by manufacturers typically does not include a rear ladder, or a bumper mounted
spare. Some manufacturers include the length of an extended pin box, but others don't.
Example: our 265RL is listed as 30 ft long... the actual length is 32 ft, from the king pin
(including the extended pin box) to the rear (including the spare).
We reserve a campsite at 32 ft minimum.
Hope that helps,
Terri, the co-pilot