This set of coasters is perfect as a puzzle to solve for your guests at a party. The challenge is to place the nine coasters in a 3 x 3 pattern so that the number of dots in each row, each column and each diagonal is identical. This is known as a magic square. For more information about magic squares, see my blog or search on the web. The coasters are beautifully handcrafted in Sweden using high-quality beech wood. The coasters have a wooden through insert which forms a unique and eye-catching look. The pattern for numbers one to nine has been created based on the pattern of a regular dice.The coasters are perfect for protecting your coffee or dining table from spots and stain caused by moisture or heat from cold glasses or hot coffee or tea cups. They are coated with a hydrophobic finish. Thin cork pads are attached to the back side in order to protect table.