Many wireless carriers offer Voice over LTE, or VoLTE, a feature that’ll get you higher quality voice calls and other improvements over traditional voice calls. And now we can add Google’s Project Fi to the list of services that offer VoLTE.

Google has confirmed that it’s now testing VoLTE calls on Project Fi. Only a “subset” of Project Fi customers currently have the feature, though. To tell if you have VoLTE, check your signal indicator when you’re on a phone call; if it shows LTE instead of H, you’re on a VoLTE call.

Project Fi customers with VoLTE will get higher quality calls as well as a faster call setup. These customers will also enjoy faster data speeds if they’re browsing the web while on a call.

VoLTE offers several improvements over normal phone calls, so it’s good to see that Google is now testing the feature with Project Fi. There’s no word yet on when the feature might launch to all Project Fi customers, though, so if you’re on Fi and without VoLTE, you’ll just have to sit tight while Google continues its testing.