EXcap 110 is a set of optical reference filters for verification, adjustment or calibration of Exner-NIR sensors. This set can be equipped with up to three individually selectable single filters to verify the corresponding sensors in their ideal measuring range. The optical filters can be easily attached on to the measuring gap and they are optimally fixed during verification or calibration. The optical filters are traceable according to NIST standard and can be verified at the factory.