It was agreed with the head of the astronomy department of the ING that filters from the ING and the NOT can be offered to both communities. On the respective filter web pages links are provided with a text stating that filters from the other observatory might be used. The handling of the filters themselves, i.e., the responsibility for collecting, maintaining and returning the filter will be with the observatory that borrows the filter.
There was some confusion about the proper cleaning of filters, and instruction were defined and posted on the web.