The Stens Pre-Filter for Stihl Cutquik Saws improves the efficiency of your equipment by capturing dust and large particles before they reach the main filter. With a pre-filter in place, the main filter can do its job of capturing smaller particles without getting excessively overloaded with larger contaminants. Using a pre-filter will extend the life of the main filter, which has a finer mesh that can tend to get clogged quickly if exposed to too many particles at once. Extending the life of the main filters is helpful because they tend to be more expensive than pre-filters, and most pre-filters can be cleaned several times before they need replacement. Stens pre-filters are made of high-quality materials that effectively capture dust and other particles.