Google is finally diving into 4K Ultra HD movies: Starting Tuesday, Dec. 6, Google Play Movies now offers about 125 titles for purchase in 4K, which offers four times the resolution of 1080p HD.

But for now, the 4K movies available only to consumers in the U.S. and Canada, and only on a small number of playback devices — and as much as anything else, the push looks aimed at driving sales of Google’s 4K-enabled Chromecast Ultra, which went on sale last month.

Movies now available for purchase in 4K on Google Play include: “Batman v Superman: Dawn of Justice” (pictured above), “Ghostbusters,” “Mission: Impossible – Rogue Nation,” “Captain Phillips,” “10 Cloverfield Lane,” “Lucy,” “Everest,” “The Lego Movie,” “The 5th Element” and “The Amazing Spider-Man.”

The 4K titles can be purchased from Google Play on Android devices or on the web and streamed on Chromecast Ultra, Sony Bravia Android TV, or Xiaomi Mi Box 3. In a limited-time promotion, the internet giant is offering a free 4K movie to owners of a new Chromecast Ultra (priced at $69), who also can get HBO Now free for three months free.

Content in 4K Ultra HD remains relatively scarce. Amazon.com and Vudu offer a selection of titles in 4K, while Apple’s iTunes does not yet offer TV shows or movies in the format. Among subscription-streaming services, Netflix and Amazon Prime Video have offered some 4K content for several years, and Hulu last week launched 4K Ultra HD titles original series including “The Path,” “11.22.63″ and “Chance” and 20 James Bond movies. Also last week, YouTube launched support for live 4K video streaming.

Google Play is compressing the 4K movies using VP9, an open-source codec backed by Google, which is also used by Netflix for its new download feature for select titles.

Also Tuesday, Google announced that the Google Play Movies & TV app is now available on 2016 model Samsung Smart TVs. Titles in customers’ Google Play libraries are immediately available to watch directly on the Samsung connected TVs.

In October, the company launched Google Play Movies & TV on the Google Daydream View virtual-reality platform. That lets users watch all the movies and TV shows in their Google Play library in a “virtual cinema,” even if they’re offline.