I worked in a small casino in russia that bought some wheels off a rival operator in the town. We had two roulettes and the rival operator used to come in and play but only on the one table. he mostly used to play 23 and the neighbours, but big bets and always seemed to win regularly walking out with 2- 4 thousand. during one day shift i took a careful look at the wheels and noticed that the number 23 and the numbers either side had slightly larger compartments than the other numbers and than the same numbers on the other tables wheel. So during the day i switched wheels and when this guy came in on the evening he ended up losing 16000 dollars left in tremendous temper and never came back!