Specifications: Astrosital (Russian equivalent to Zerodur) is a glass-ceramic material with ultra low thermal expansion. It is widely used as substrate material for astronomic mirrors. Maximum available size:500 mm Dia. -------------------------------------------------------- Windows, lenses, prisms, mirrors, filters, substrates, wedges for ultraviolet, visible and infrared spectral regions made from kbr, nacl, kcl, csi, caf2, baf2, lif, mgf2, znse, sapphire, SI, ge, optical glasses, astrosital and fused silica. We produce both blanks and polished details with optical coating as well. We make 100% input control of all raw material we use in the production of our details. Our products have certificates of quality. We have special equipment for quality control of the details.