Google Play Movies & TV app will soon let consumerrent or buy titles in the highest quality available (4K), allowing those with 4K televisions and a Chromecast Ultra to take full advantage of their capabilities. Here are the purchase options:

Rent UHD: $7.99
Buy UHD: $24.99
(watch 4K on Chromecast Ultra and UHD Android TVs)

Rent HD: $3.99
Buy HD: $12.99
(watch HD on this device and on Chromecast, Chrome browser, Roku, and most other Android devices)

Rent SD: $2.99
Buy SD: $9.99
(watch SD on the web and supported devices)