They are made of plastic with a small strong neodymium magnet at the bottom

and they can sit on cars going as fast as 120 km per hour (tested on Jutland's motorways)

The packaging is in German

And the pull force of 245 kg

Magnetiske tal extra 1 - Magnetfolie 10x15 cm. (4-pak) Tier1 They are made of plasticWhite magnetic foil with black number "1" printed on the front. Each number is A6 size (approx. 10x15 cm.) and this is a pack of 4 additional number 1s. Great for time, date and calculations on magnetic boards. Colour of magnetic foil: White. Colour of numbers: Black. Thickness: 1 mm. Strength: approx. 80 g. cm2. Content: the number 1 (4 pcs.) Magnetic sheets are made of magnetic foil and can adhere magnetically on metal cabinets, whiteboards and