4 in x 1.3 in x 0.13 in / 10.2 cm x 3.3 cm x 0.3 cm
Have someone pick a number from 1 to 16 and these amazing alder wood cards will quickly determine the number.
The secrets of these long lost cards were found in a 1942 book by Maurice Kraitchik called Mathematical Recreations. They are also called window cards and have a fun magical edge to them. Each card is 1.3" x 4" x 1/8" thick alder wood with the numbers and text deeply laser engraved.