The Hilti VC40-U vacuum (Hilti, Inc., Tulsa, OK) (Figures 2 and 3) was tested in combination with the Hilti DC-EX 125/5 Dust Guard (Hilti, Inc, Tulsa, OK) (Figures 2 and 4) attached to Hilti grinder.. The vacuum is specified to weigh 32 pounds when empty and to provide 129 cubic feet of air flow per minute (cfm). The vacuum has a filter and a device that automatically cleans the filter with a ...