Best answer: USB Power Delivery, or USB-PD, is a protocol specification that supports power delivery up to 100W while using a single cable. It allows a range of devices, including Apple's Smart Battery Case for iPhone XS, iPhone XS Max, and iPhone XR, to charge faster.The power source: 87W USB-C Power Adapter ($79)The connector: USB-C to Lightning Cable (2m) ($35)For the iPhone XR: Smart Battery Case ($129)For the iPhone XS: Smart Battery Case ($129)For the iPhone XS Max: Smart Battery Case ($129)