The Day & Night Plus is the new design which does not snap in to a deck plate like the original Day & Night 2000 did.
They are a fixed mount unit which fastens to the mounting surface without the use of a flanged ring used by the previous version. If replacing the Day & Night 2000 with the Plus, then the white deck ring for the original vent must be removed in order to install the “Plus” model.
They are taking the place of the snap-in vents which have been discontinued. The Day and night Plus will fit in the same cut out.