The Diffuser for Makita® 11 Gallon Wet/Dry HEPA Filter Dust Extractor/Vacuum (VC4210, sold separately) controls the exhausting airflow to minimize dust entering the motor. It also dampens the vacuum noise for quieter operation. The optional PTE Flat Filter (W107418351, sold separately) is available for added protection of motor and prolonged vacuum life. The Diffuser installs quickly and easily for added user convenience.