Unlike a lot of similar tents that only go on the roof, this one installs on the bed rack and folds away into an aerodynamical hardshell case, so it shouldn't reduce your truck's range.

for its Mammoth 900 or Mammoth 1000 Ram TRX truck builds ... Hennessey basically outfits the bed of its Mammoth 1000 TRX with a rack and roof top tent, both "essential" for the quintessential ...

This is like a portable cabin for the bed of your electric or ICE truck ... Since there's no cabover section, you could also add a roof rack (maybe a roof top tent?) to lug around more stuff.