This is a Hextek lightweight gas-fusion mirror. It weighs 49.6 lbs, and measures 17" x 24" x 5" overall. An area of 16" by 23" is layered with a high reflectivity dielectric coating which is optimized for a wavelength of 248 nm. However, the mirror could easily be over-coated with some other material. As shown in the interferogram below, the surface peak to valley is approximately 400 nm.