The 05D20BD.1 Broadband Dielectric Mirror is an extremely versatile mirror for laboratory applications and highly efficient over a broad wavelength range. This 1/2 inch (12.7 mm) diameter mirror is made from a 3.1 mm thick Borofloat® 33 substrate. Borofloat® 33 has low thermal expansion and is an excellent substrate for most applications. The BD-1 coating is extremely durable and will withstand repeated cleaning. This mirror has a λ/10 surface flatness and a 15-5 surface quality.