Anderson goose neck adaptor hitch.

N-Trouble already corrected the spelling (Andersen with an "e") - I'll just chime in and say that the Andersen Ultimate system is not a "gooseneck adapter" - it's a completely different animal. What Andersen does make, though, are several models that attache to the truck using your existing gooseneck ball. The engineering differences being that a true gooseneck adapter puts forces on the pin box and front of the frame that fifth wheel RVs are not designed to take. The Andersen Ultimate involves the same forces as a standard fifth wheel hitch. We pulled our first 12K miles full-timing in a 14,000 lb. GVWR fifth wheel with one and really like it.

Rob

Just search on Andersen here. Lots of discussion on here the last couple years. There are a handful of critics (non owners) of the hitch but a lot of satisfied owners. I have the steel GN version and have been very happy with it. My 5er Toyhauler GVWR is 12k lbs

Those that use them, love them.

Those that don't have a myriad of reasons it's unsafe in some way and they'll never use them.

Doesn't seem to be much in-between.

http://learntorv.com/hitch-options-for-your-fifth-wheel/