Are the lenses polarized?

No. The RB4259 uses non-polarized brown gradient lenses, so glare off water and roads is reduced by tint but not blocked the way polarized lenses block it.

What does the 51-20-145 sizing mean?

It is the lens width, bridge width and temple length in millimeters: 51 mm lenses, a 20 mm bridge and 145 mm arms. That puts it in a medium fit.

What comes in the box?

A hard case and a cleaning cloth are included with the sunglasses.

How does it compare with the Ray-Ban Round Metal?

The RB4259 is lighter and molded in nylon rather than metal, and it has a keyhole bridge instead of adjustable nose pads. The Round Metal offers metal build and more fit adjustment.

Is the brown gradient lens good for driving?

It handles everyday daylight well, but because it is non-polarized and gradient-tinted, it is a weaker choice for harsh glare on the road than a polarized lens.