21+3 are optional side bets, available in some twenty-one casinos online and live casinos. 21+3 uses the dealer's faceup card and the player's first two cards to determine a winner. Although the 21+3 side bets (5 different ones) have a higher house edge, they also have higher payouts:
Three of a kind (suited) - 100:1
Straight flush - 40:1
Three of a kind (unsuited) - 30:1
Straight - 10:1
Flush - 5:1