https://www.techradar.com/news/oneplus-6-doesnt-have-wireless-charging-yet-has-a-glass-back-heres-why

The new OnePlus 6 has almost everything you'd want in a flagship phone for a very affordable price, but it is missing one feature we expected: wireless charging.

It's surprising because the OnePlus 6 has a glass back, a switch from the aluminum shell on the OnePlus 5T and all OnePlus phones before it (except the old OnePlus X).