Dual Sim Card Tray - OnePlus 6 User Manual

Dual SIM Card Tray

The OnePlus 6 is carrier-unlocked out of the box, with dual
nano-SIM card support. With the power to connect to two networks
at the same time, you can use one device for everything.
Control how you connect to the world by adjusting your SIM and
carrier permissions and restrictions using SIM & Network Settings
found under Settings.
Use the SIM Tray Ejector (found in the box) to remove the SIM tray
from the device. Up to two Nano SIM cards fit in the tray.
9 | What's in the Box Device OxygenOS Safety Information