In the receiver, you will be using some sort of hitch ball Mount. It incorporates a shaft that fits to the Receiver, locking by using a Hitch Pin and a hole by which to attach a Hitch Ball. In the case of towing an Airstream, the mount is the http://what-size-hitch-ball-do-i16050.vblogetin.com/10101257/the-ultimate-guide-to-what-size-hitch-ball-do-i-need-for-a-travel-trailer