This tool is used to unscrew 2" filters that are difficult to access. It was originally developed for the Baader 2" Cool Ceramic Safety Herschel Prism Mark II (Visual / Photographic) (different versions / variants available) to make it easier to replace the installed filters and is designed for all current Baader 2" filters with low-profile mount. Fit not guaranteed with older filters. The "filter crown wrench" is specially designed for all Baader 2" filters installed in housings. This is due to the unique design of our filter housings, which have a precisely milled "filter crown". The filter crown wrench interacts with this special notch and is only effective when used correctly. Due to these features, the tool is not compatible with filters from other manufacturers. This crown wrench is 3D printed. Owners of 3D printers can also find the print file in our download area.