Unfolded, this "not a phone" is wicked thin—just 4.9 mm. For comparison, the famously so-thin-it-bends iPhone 6 Plus was 7.1 mm.

While it is a non-phone, the Duo features a removable SIM like other Surface devices. (No handy trap doors here, though.)

When folded, the Duo undercuts Samsung's original Fold by 7 mm (9.8 mm thick vs the Fold's 17 mm)—ludicrously thin, if less pocketable than, say, the Moto Razr.

The hardware honeymoon ends as we try to use the dysfunctional software to load a web page. Crashes, flashing screens, and flickers galore!

Thankfully, Microsoft has promised three years of software updates for the Duo—long enough to iron out lots of kinks. But will this ultra-thin, all-glass slab last that long in your hands?