Water circulation vac pump for bho

[cyclopath]

tell us why you picked this one.
give us all your reasons.

what does 680mmHg mean to you?

Has anybody used this digital vacuum guage?

and just to clarify, thats 1mm Hg => 1000 microns Hg (because 1mm = 1000microns) why do we measure Vac in Hg?