The new foldable iPhone Duo is the "thinnest iPhone ever," according to Apple. When unfolded, the device is 5.2mm thick, making it 0.4mm thinner than the 5.6mm iPhone Air. Rumors suggested it could be as thin as 4.5mm when unfolded, similar to Samsung's Galaxy Z Fold8, but it didn't end up that thin. At 5.2mm, it's just a little bit thicker than the 5.1mm 13-inch iPad Pro, which is Apple's thinnest device. When folded, the iPhone Duo is 11.3mm thick.