It is the II. I wanted the speed adjustment and in/out capabilities. Super easy in the bath. Just tapped into the power wires for the light. In the main area it is a little harder to get the wires but there is a bundle of them running along the fan opening. Hardest part is making sure you hit a constant power wire and not the one that runs the main cabin lights from the switch. Other than that getting everything to line up in the opening would be the next challenge but not too bad. I managed to do it alone in about 20-30 min. per fan. We have a seasonal site at a sailing club and can't use the AC so I am hoping this keeps us cool with a nice airflow all summer long!