This Nilfisk Microfilter is like a white fabric bag, fitting over the bottom of the motor. It retains 99.5% of all particles to 2 ?m, cleaning the air quite well before it reaches the motor and final ULPA or HEPA filter. It should be replaced after you use ten paper bags to keep your Nilfisk performing well. Nilfisk has replaced this filter with their similar 117304-10 filter. For similar products see our list of current Nilfisk Vacuum Supplies.