If you're in a hurry, here's a teardown TL;DR in X-ray form—courtesy of Creative Electron.

Those of us without X-ray powers can only see this pristine, polycarbonate exterior.

The polycarbonate build should be more durable than a glass back, although it's likely no match for the rigidity of the metal construction of yore.

One thing has persevered through the Pixel's changing materials—the partial matte finish on the back.

Meanwhile, this Pixel's party piece—a rear camera like the one in the rest of the Pixel 3 line—promises some serious firepower for a budget phone.

Turning to the front of the phone, we note how this notch-less 3a has bezels similar to the standard Pixel 3, but has just one front-facing camera.