Apple’s just-announced iPad Pros are making the switch to USB-C, and with that switch comes a nifty new feature: you’ll actually be able to use your iPad to charge your iPhone on the go, making it the world’s most expensive battery pack.

Just plug in your iPhone (or, presumably, any other device that you want to charge) into the iPad’s USB-C port, and it’ll charge. Apple hasn’t said yet what kind of power that iPad will be able to push — you probably won’t be able to charge another iPad Pro or a Mac, for instance — but if you’re out and about and you need some extra juice for your phone, it’s a neat option to have.

Of course, you’ll still need to buy a USB-C to Lightning cable for an extra $19.99, since Apple still doesn’t include them in the box with any iPhones.