Review on Revitalize Your Cabin Air Filter with K&N's Cleaning Kit: Sprayer Bottle Cleaner & Refresher Kit; Enhance Filter Performance; Service Kit-99-6000, 99-6000AMZ by Nathan Jankowski

Pretty straightforward. You will be given a cleaner and oil to restore the filter. Clean until water runs clear, let dry, spray on oil, reinstall. Most cabin filters are around $30, which is about the same as a new K&N. So this conversion kit should last 3 or 4 years and you typically clean this filter once a year as needed. For a filter and rebuild kit that costs about $40, after 4 years expect to be about $10 a year. After 8 years $5 per year. After 16 years $2.50 per year. It's quite a nice deal if you keep up with the times and your filter element doesn't get damaged. Note that this filter will not filter as efficiently as a new HEPA cabin filter and will not be able to filter out odors like carbon filters. Just something to note. The oiled element performs quite well and seals my car's HAVC air intake better than a paper filter. So this should prevent much of the filter bypass that can occur with most paper or fiber filters. Of course, if you have a K&N cabin air filter, this is a good buy.