BK7 is a high quality optical glass that is used whenever the additional benefits of fused silica are not required. Since BK7 performs well in all chemical tests, and no additional or special handling is required, costs of manufacturing are reduced. It is a relatively hard material with extremely low bubble and inclusion content, while providing excellent transmittance through-out the visible and near infrared spectra and down to 350 nm in the ultraviolet.

For all standard optical glass components, or when optical glass is generically requested for custom elements, Tangsinuo uses normal high quality BK7 optical glass.