100% tested; each pieces is supplied with an interferogram
High-efficiency broadband coating averages 96% reflectivity.
Made from precision annealed Pyrex.
Protostar large Pyrex secondary mirrors are supplied with interferometric test reports, and are 0.1 p-v surface flatness or better (measured at 650 nm wavelength, and evaluated edge-to-edge.) Surface polish is rated at 40-20 scratch/dig. Made in the U.S.A.
Note: Smaller secondary mirror sizes are available as ULS Quartz secondary mirrors.