When considering the physical design of a smartphone, there's one key dimension that often matters most to the majority of users: thickness. No one wants to carry around a thick, clunky smartphone. Manufacturers realize thin devices sell, which is why it seems every time we turn around they're constantly fighting for the title of thinnest device.

The current title-holder is the Motorola Droid Ultra, which is billed as the thinnest 4G LTE smartphone. It measures just 0.28 inches thick and is available exclusively through Verizon Wireless...