With over 36,000 REDBOX locations around the United States, each REDBOX holds up to 700 optical discs which are a mixture of 4K Blu-ray, standard Blu-ray, and 480i DVD discs. In many smaller cities and some rural areas REDBOX now has around 3 different 4K Blu-ray titles to rent for $2.50 each (some larger cities might have 6 different 4K Blu-ray titles that are stocked in each machine). Plus, several dozens of 2K Blu-ray titles to choose from for $2.25 each. Plus, 480i DVD discs. Technically REDBOX could stock around 700 different titles in each machine if they wanted to give the best amount of choices, however when new releases are offered in three different optical disc formats and if the demand is high for that new release perhaps 12 or more of the same titles need to be stocked in each machine. But less popular older releases 1 title for each machine gives the ideal selection.
When at a REDBOX machine one can search by which optical disc format one is interested in to see all the 4K Blu-ray titles, standard Blu-ray titles, or 480i DVD disc titles.
https://www.redbox.com/