Amazon is adding audio content from its subsidiary Audible to Amazon Prime.
Amazon is adding more benefits to its subscription service, Prime, on Tuesday. The e-commerce giant said Tuesday that Prime members would now have unlimited access to podcasts and audio from Amazon-owned Audible.
For $99 per year, Amazon Prime members can access and stream digital movies, TV shows, and Amazon’s original productions in addition to receiving free two-day shipping and one-hour delivery on certain orders. According to a recent Consumer Intelligence Research Partners report, Prime has 54 million U.S. members, up 35% from 2014. Furthermore, 38% of American households are members, according to research from investment bank Cowen. Amazon has historically declined to reveal how many Prime members it has in the U.S., but has said publicly that it is in the “tens of millions.”
With Tuesday’s news, Prime members will now able to stream a rotating selection of more than 50 audiobooks. Prime members will also have free access to Amazon’s newly launched on-demand audio service from Audible, Channels, which provides ad-free podcasts and other audio content. Audible released the service in July, and is charging non-Prime members $4.95 each month to access the selection of podcasts.
Get Data Sheet, Fortune’s technology newsletter.
In addition to podcasts, Channels also includes access to audio versions of articles from major publications, comedy shows, short fiction, and more.
Like with Prime Video, Amazon is letting members access exclusive, Audible-produced audio content such as Ponzi Supernova, a podcast detailing the crimes of financial criminal Bernie Madoff, which includes jailhouse interviews with Madoff himself.
It’s not particularly surprising that Amazon is adding more content to the Prime membership. Amazon Prime has emerged as one of the key pillars of the company’s e-commerce and streaming businesses. According to The Wall Street Journal, Prime customers spend as much as double on purchases on Amazon.com to what non-Prime customers spend in a year. And Amazon has been looking for more ways to include exclusive video content into Prime memberships benefits, so it makes sense that audio content is part of that push as well.