This side bet offered in some single-deck games allows you to wager on whether you will be dealt two cards of the same suit. If so, you will be paid 3 to 1; if you are dealt a king and queen of the same suit, you will be paid 10 to 1.
A card counter developed a system for beating this rule a few years ago, which he sold privately for a few months, then took off the market. I examined the system, and also had the theory tested via computer simulation, and it worked! Unfortunately, it was not an easy card counting system, as you had to keep four separate counts of the cards remaining in each suit. Most casinos that offer the Royal Match option restrict the maximum bet, usually to $25. This limitation makes it difficult to make much money with this option, except for camouflage as player advantages do not occur very frequently. Since any Royal Match counting system would prove worthless for all normal playing and betting decisions, it will rarely be worth a player’s time or effort to attempt to exploit it. And do not bet on this option, except for camouflage, unless you are using a valid suit-counting system, as the house edge is 3.8%.
Some casinos also offer a multiple-deck version of the Royal Match bet where any first two suited cards pay 2 1/2 to 1, and a suited K-Q pays 25 to 1. This is far worse for the player than the single-deck version—with these multi-deck payouts, the house edge goes up to 6.7%, and no suit-counting system will beat it.