Well, it isn't Max because they don't have those Universal Hitchcock movies. In my personal experiences, Amazon Prime is by far the worst streaming service. Furthermore, Amazon has been known to mislabel movies in regard to the 4K format. I rarely stream anything from Amazon. For the most part, it's either iTunes or Vudu.I'm on Prime and have Max, so I guess it's one of those two. All I know is, three days ago they didn't have the UHD and yesterday they did. They still don't have the others in the set in UHD so I'm wondering if they jumped the gun in listing it that way but still using the older transfer. I'll finish watching tonight.