The 402976M Dust Extraction Attachment for Cordless Rotary Hammer DH18DBLP4 is a self-contained unit with a HEPA filter that is compliant with OSHA's silica dust exposure regulations It captures 99. 97% of particles 0. 3 microns and larger. This unit has a guide hole designed to align with the hammer and bit for accurate drilling. It connects to the hammer drill body and uses the power provided by the battery. This attachment has automatic power off with a three second delay, allowing for the unit to collect any remaining dust.