Product review (1 stars): Dryer cannot be pushed back all the way
Most dryers have a recessed space at the bottom rear to accommodate the dryer vent.  This allows the dryer to be pushed back near the rear wall.  This box is tall.  Taller than the recessed area.  So the dryer must sit forward 4 or more inches off the rear wall.
For the magnet to stick, the box is made of sheet steel.  Heat and humidity will over time rust the best-painted sheet steel so this will probably last only a few years.  That's why dryer vents are typically made of aluminum.
The magnets are wimpy and the black hexagon you see is a rubber piece that holds the magnets.  There is no back on the box so you can't exit from the rear.
BTW, this is less expensive direct from the manufacturer.