This fitting fits into either side of the paper bag models.  The paper bag fits snugly on the fitting up to the line indention.

STANDARD FOR PAPER BAG UNITS,
OPTIONAL when converting a cyclonic unit to paper bag
This new inlet stem has been designed to make the installation and maintenance of our power
units easier. Use this inlet stem in place of where you previously inserted a piece of PVC tubing into the hole in the side of the power unit.
To install: Choose the side of the unit that you would like to connect your tubing to.
Insert the inlet stem all the way into the canister. There is a small hook that protrudes
from the flange of the inlet stem. Rotate the inlet stem so that the hook on the side of
the flange lines up and points to 9 o’clock. Then, attach clamp
coupling to the plastic inlet stem by tightening the screw on the coupling. Your PVC
tubing will attach to the other end of the clamp coupling.

Additional information