Nilfisk central vacuum self cleaning permanent filter is washable and durable. Intended to last the life of your central vacuum machine.  Designed to fit the Nilfisk Supreme 150 & 250.  This filter allows the consumer to use their central vacuum machine with or without a bag.  It’s made from a heavy-duty fabric and flexible rubber. Intentionally designed to seal your central vacuum bucket system and protect the motor from dirt and debris.  With a weight deliberately installed in the center of the fabric to help remove the dust from the filter.