In recent years, set-top boxes have been shrinking down to tinier, cheaper packages with a growing list of fun new features. The new Fire TV dongle with 4K, HDR, and Dolby Atmos showcases some of the best aspects about this trend. It's cute. It's a thrill to use. It's just $US70. The only problem is that you still can't use the new Fire TV for everything. It's very good, but it's not the very best.