The 05D20ER.1 Broadband Metallic Mirror is an excellent general purpose, broadband reflectors. 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 ER.1 enhanced aluminum coating may be used wherever a broadband visible and near infrared reflector is needed. A multilayer dielectric stack deposited over the aluminum film boosts reflectance and improves the durability of the coating. Average reflectivity is greater than 93% from 450–700 nm. This mirror has a λ/10 surface flatness and a 15-5 surface quality.