Acrylic is a scratch-resistant plastic, available optically clear or opaque. It is often used for tanks, panels, and optical applications.  It can be somewhat brittle in thin walled areas, so it is not recommended for delicate or complex geometries.

This plastic is also known as PMMA, an abbreviation of its full chemical name, polymethyl methacrylate, as well as by the trade names Plexiglas and Lucite.

Acrylic is transparent or opaque (black, white, and a variety of colors) in its unfinished state.  Clear acrylic will take on more of a frosted translucent appearance when machined, though can be smoothed again to an optically clear state using various finishing methods.