Very small Backgammon dice including a 10mm doubling cube. Other dice are 2 black and 2 white standard 6 sided dice but they are also very tiny. See picture for reference (penny not included).

The rules for using a doubling cube are simple. Although similar to a standard die it has the numbers 2, 4, 8, 16, 32 & 64 printed on the sides. The cube starts off not controlled by either player but once a player believes they have an advantage in the game they may offer a double before rolling the dice. The opposing player must either accept the double or concede the game. If the opposing player accepts the double then the point value of the game are doubled and the die is turned to reflect that amount. When a player accepts a double he or she now had control of the doubling cube and only the player currently in control of the cube can offer a double.