Dominoes spots from one to six are generally arranged as they are on six-sided dice, but because blank ends having no spots are used, seven faces are possible, allowing 28 unique pieces in a double-six set. However, this is a relatively small number especially when playing with more than four people, so many domino sets are "extended" by introducing ends with greater numbers of spots, which increases the number of unique combinations of ends and thus of pieces. Each progressively larger set increases the maximum number of pips on an end by three, so the common extended sets are double-nine, double-12,
Dominoes of a black-hooded robe and a white mask. Despite the coinage of the word polyomino as a generalization, there is no connection between the word "domino" and the number 2 in any language. European-style dominoes are traditionally made of bone or ivory, or a dark hardwood such as ebony, with contrasting black or white pips (inlaid or painted). Alternatively, domino sets have been made from many different natural materials: stone (e.g., marble, granite or soapstone); other hardwoods (e.g., ash, oak, redwood, and cedar); metals (e.g., brass or pewter); ceramic clay, or even frosted glass or crystal. These sets have a