Once the M-Vac collection is done, the sample typically has tens if not hundreds of ML of solution, so the sample must be concentrated.  This is the second step of the M-Vac process and it involves a .45 micron or a .22 micron PES filter apparatus that operates under the same vacuum pressure that the collection process works.  The extension tubing is detached from the M-Vac collection head and attached to the filter apparatus, then the user turns on the vacuum and slowly pours the collected liquid into the filter chamber.  The liquid passes through the filter, while the DNA material will be collected on the non-binding PES surface.  Filters come individually and in cases of 12.