https://www.techradar.com/news/oneplus-6-to-be-made-from-new-materials-according-to-teaser

The OnePlus 6 is sure to be an upgrade on the inside, but it could also sport some significant changes on the outside, as OnePlus has posted a new teaser on Twitter saying that the phone uses new materials.

They haven’t said what those materials might be, but some earlier leaked images from ITHome show the phone with what appears to be a glass back, which would be a change from the metal-backed OnePlus 5T.