In Roulette, selecting 12 numbers to bet on is almost one third of the numbers on a European wheel since, aside from the one green Zero, there are 36 numbered pockets, 1-36, organised on the betting layout as 12 numbers in each of the three Columns and 12 numbers in each of the three Dozens.

In American roulette, the table has tiles labeled 1st, 2nd and 3rd. The corresponding drawers on the French table are arranged in two areas and labeled 12P , or Premier Douzaine (numbers 1 through). 12), 12M , or Moyenne Douzaine (numbers 13 to 24) and 12D , or Dernire Douzaine (nos. 25 to 36).