One of the big advantages of the Dustless HEPA Wet/Dry Vacuum is the optional Micro Pre-filter that greatly extends the life of the HEPA filter. The Micro Pre-filter is an inexpensive disposable filter that captures the vast majority of the dirt and dust before it reaches the more expensive HEPA filter. In fact, the Micro Pre-filter captures particles down to .5 microns. That’s remarkably close to the HEPA filter that captures particles down to .3 microns.