Comcast is making it easier for its broadband-only customers to access streaming video without an outside set-top box.

For $5 per month, Comcast will give its internet-only customers a connected box to watch Netflix, Amazon Prime and other streaming applications, eschewing the need for a separately purchased device such as a Roku, Apple TV or Amazon Fire TV. Called Flex, the device and service will be available for Comcast customers on Tuesday.

Flex will only be available to Comcast internet customers. It will come with a voice-activated remote, allowing internet subscribers to find content in a similar fashion to X1 customers. CNBC first reported that Comcast, the largest U.S. cable company, was developing a device in November.

Comcast has already integrated streaming services such as Netflix, YouTube and Amazon Prime Video into its X1 platform for customers who purchase cable TV. The new product won't give customers access to TV channels in the pay-TV bundle, but it will give customers the option to rent shows and movies and upgrade to a Comcast video package. The Flex box also only works if you lease a Gateway router from Comcast, which costs an extra monthly fee.

Flex won't include livestreaming services that compete with Comcast, such as Sling TV and DirecTV Now, said Matt Strauss, executive vice president, Xfinity Services for Comcast Cable, on a media conference call.

"Xfinity Flex will deepen our relationship with a certain segment of our Internet customers and provide them with real value," Strauss said in a statement. "For just five dollars a month, we can offer these customers an affordable, flexible, and differentiated platform that includes thousands of free movies and shows for online streaming, an integrated guide for accessing their favorite apps and connected home devices, and the ease of navigating and managing all of it with our voice remote."

Strauss said pricing for Flex could change in the future as Comcast experiments with different pricing tiers and packages.

Disclosure: Comcast is the parent company of NBCUniversal, which owns CNBC.