This is a pack of 10 of the very popular 05D20AL.2 Broadband Metallic Mirrors. This 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 AL.2 UV enhanced aluminum coating is a durable, broadband UV reflector with average reflectivity greater than 90% from 250–600 nm. The aluminum film is overcoated with UV transparent magnesium fluoride to prevent oxidation of the metal. This mirror has a λ/10 surface flatness and a 15-5 surface quality.