The Spectrolino comes equipped with three different filters
To switch your filter, turn the filter tube counterclockwise until the arrow on the filter aligns with the arrow on the Spectrolino. You should be able to easily remove the filter from this position. Align the arrow on the new filter to the reference point and turn clockwise until the end of the mark. The filter should now be snugly in place.
After you change your filter you will need to perform an absolute white calibration.