This pack of six (6) magnets are designed to be used with the Revitalizaire Magnetic Vent Covers. This pack can be used when your register configuration requires additional magnets. Floor Registers: Usually no magnets required unless very strong airflows are present. For these cases, 1 magnet per cover, located in the center should do the trick. Wall or Ceiling Registers: Between 2 and 4 magnets will be required per sheet. This will depend on the amount of metal surface area of your register as well as airflows.