Asus is unveiling the PadFone X today, the first of its transforming PadFone devices that's headed to a major US carrier. Though there's no word on exactly when it'll come to the US, AT&T has announced that it will eventually begin carrying the new device. That isn't the only first for this phone though: when it does launch on AT&T, it should be among the first devices with support for Voice over LTE (VoLTE). Whether or not AT&T will actually enable VoLTE at launch isn't clear, but the PadFone X will be ready for when it does.

A smaller gap between phone and tablet

Full details for the PadFone X haven't been revealed yet, but it looks almost identical to its predecessor. It has a 5-inch, 1080p display, and a similar black body with silver metal highlights. It's running on Android 4.4 and includes stereo speakers and NFC, but that's all we know for now.

Like its predecessors, the PadFone X's standout feature is its ability to dock inside of a companion tablet that effectively uses the smartphone as its brain. That ability to transition from smartphone to tablet — and to use one data plan across two devices — has been the PadFone's big appeal, but Asus is making the difference between phone and tablet a little bit smaller this year. Rather than docking into a 10.1-inch tablet like its predecessors do, the PadFone X docks inside of a slightly smaller 9-inch tablet.

The PadFone's promise of letting users easily move apps and files between different types of devices has always been an appealing one. But with performance being one of its biggest limiting factors in the past, we'll have to wait to see the PadFone X's full specs before getting a sense of whether it'll finally be the phone to make it all work.