These filters offer far superior filtration than the traditional Knosti 3 filter system. To use these you will need to lay the filter tray on top of one single filter, centralised, fold the four edges over on top and then fit into the funnel. This provides a tight fit and no chance for the fluid to bypass the filter. Pack of 3 filter sheets (filter equipment not included) for max 9 uses (3 per filter). They stop filtering when clogged with dirt. The 3rd use takes considerably longer than the first.I have repeatedly tested this method and give it my personal endorsement. Don't tell anyone about these filters though, they make the fluid last longer.