Someone else would know better but afaik, this is the first four discs from the six disc set. So you lose out on the special features, but you get the different cuts of the movies and commentary tracks, same mastering, I think. To me, I barely have enough time to watch the main features so paying double for two, admittedly amazing looking, discs of extras I'll probably never watch didn't make sense. Again, someone else will correct me if I'm wrong on the details here. It's annoying how confusing companies have to make this shit. Just put the stuff out and stop making seven different versions of every damn thing.