The middle glass portion is likely to have a fingerprint sensor underneath it. (dealntech.com)
We're looking at rounded corners, a metal body and a strange glass portion that covers much of the back of the phone. (bgr.com)
At rear, the general motif has been carried over from the original Pixel XL: a matte metal surface for most of the rear and an enclosed glass portion at top. (pocketnow.com)