So the inline fan is in addition to the airflow boost?A. The Imperial N1930BP has dual blowers in the housing of the insert, the "booster" is just a wider collar to allow for more airflow.
What does it mean to purchase it with the in-line fan?A. That customer meant he purchased an in-line fan with it. Meaning he bought a in-line (air duct fan you place in your duct), to help move the air faster, thus creating less noise.