Optical borosilicate crown glass (BK7) is the most commonly used technical optical glass for high-quality optical components in the visible and near-infrared range. It has a high linear optical transmission in the visible range up to 350nm in the UV range. The BK7 has a high degree of homogeneity with a very low number of inclusions and is almost bubble-free. It appears very clear and bubble-free. BK7 is relatively hard and shows good scratch resistance. BK7 is chemically very stable, which is why grinding and polishing are not necessary, resulting in low manufacturing costs.

BK7 is mainly used for the production of windows, prisms, lenses, substrates and other optical elements.