When we say the thumbnail sized ROSAHL ionic membrane is the world’s smallest dehumidifier we really mean it’s the world’s smallest electrical low-powered; maintenance free; long-life; vibration-free dehumidifier.
The mounting measures 24 x 30 x 5.5 mm (including terminals), but the dehumidifying element is only 6mm in diameter. From a 3V d.c. supply it uses electrolysis to provide a dehumidifying capacity up to 84mg per day from enclosures up to 2 litres.