1. iPhone 16 models in the US lack a SIM card tray, requiring users to switch to eSIMs; 2. This change is not applicable outside the US, where all models come with a SIM card tray; 3. iPhone 16 models outside the US lack 5G mmWave support, which is available in the US models; 4. eSIMs offer benefits like multiple numbers and networks on a single device; 5. Removing the SIM card tray simplifies manufacturing and improves water and dust resistance.