What I want to know is how someone managed to stretch that Heritage bag onto the opening of that 500 series Em-Tor.  It's been a while since I worked on one, but isn't the opening of a Heritage bag smaller?  Or is it that the bag spring is much tighter, making the opening smaller.  And I wonder about that 3 amp motor struggling to push the air through the more dense material on that bag.  Otherwise, it does have a certain charm!