I have been searching high and low for smart vents for my home. My home was built in 1947 and they were not designed for central air and the vents were placed in the center of the house. These are the size vents I have as far as the actual vent that sits in the sheet metal enclosure in the wall that comes out of the floor. Having smart vents would make the temperature a lot more constant and things more efficient. I have so many temperature sensors from the multipurpose sensors on every window as well as Ecobee that report temp.
Living Room: 13 1/2 X 10 3/4
Dining Room: 13 1/2 X 9 1/2
Bedrooms: 13 1/2 X 9 1/2
Bathroom: 11 1/2 X 9 1/2
Unfinished Basement: 6 1/4 X 12
Finished Basement (2): 13 1/4 X 9 1/4
Kitchen: TBD but it will be in a toe kick of a cabinet