One of the first Oculus Rift and Gear VR developers is using Google Cardboard for the latest expansion to the “Titans of Space” planet and star education experience.

DrashVR added a 50-minute narration to “Titans of Space” with a soothing male voice providing audio details of the various sights seen throughout the tour of the solar system. The add-on costs $2.99 from Google’s Play Store and works with the Cardboard version of the experience.

According to Drash, Google was chosen for the new feature because it is apparently the only VR platform currently supporting in-app purchases. So the update is Cardboard only for now.

“[I] can’t just release a separate app with narration unlocked because I have other add-ons coming as well,” Drash wrote in a message.

Audio for the first two stops on the tour are provided free and a female voice is planned to be included with the upgrade when it is available. The narration adds another dimension to what is already a go-to experience for many VR early adopters. Once purchased and activated, the narration fades in and out to match what the user is seeing throughout the tour.

The narration is provided by Michael McArdle, co-founder of The Virtual Reality Learning Experience. The North Carolina-based organization bills itself as providing “The Future of Field Trips” with VR headsets and experiences brought to local schools.

Drash separately worked with VRLE to incorporate “Titans of Space” into its educational platform.