I switch back and forth between inches and millimeters about every 10 minutes. I know that I am probably not the only user who designs with two unit systems--this usually to toggle between one metric and one imperial system. I currently change this under File-->Preferences-->Units but it would be nice if I could define two unit systems, and then have a "hot button" that would quickly select one of two "user defined" systems, maybe on the ribbon under the tool-bar and near the X,Y,Z coordinates? I Love ViaCAD, keep up the good work.