The universal microfilter filters the dust particles from the exhaust of your vacuum cleaner, providing cleaner and healthier air. To maintain vacuum cleaner performance, this filter should be changed regularly, at least twice a year or when it is visibly soiled. The filter is cut to fit and has indicator lines printed directly on the filter. So you can simply cut and fit. This pack contains one universal microfilter. ELECTROLUX universal microfilter reference: EF 2.