The Illustrious 18 and Fab 4: Playing Deviations Explained

By CardCount Academy · Reviewed October 5, 2026 · 10 min read

Basic strategy is the best play when you know nothing about the remaining cards. A counter does know something, and at certain counts a different play becomes better. These changes are called playing deviations or index plays, and the count at which a play flips is its index number.

Complete index tables run to well over a hundred entries. In 1986 Don Schlesinger showed that this is mostly wasted effort: a short list of eighteen plays captures the large majority of the gain available from all of them. He called them the Illustrious 18, and added four surrender plays, the Fab 4.

How to read an index

"16 vs. 10: stand at 0 or higher" means: with a hard 16 against a dealer ten, basic strategy says hit; if the true count is zero or above, stand instead. Below the index, follow basic strategy as usual.

Most deviations are triggered by high counts, when the shoe is rich in tens: you stand more (hitting is more likely to bust you, and the dealer is more likely to bust), double more, and insure. A few go the other way: at negative counts, with few tens left, you hit hands you would normally stand on.

The Illustrious 18

These are Hi-Lo true count indexes for a multi-deck game in which the dealer stands on soft 17, listed in roughly the order of how much each is worth.

Index numbers differ slightly between sources, rounding conventions and rule sets. Where the dealer hits soft 17, basic strategy already doubles 11 against an ace, and several indexes shift by a point. The simulator on this site applies the most common of these plays — insurance, 16 against a 9 or 10, 15 against a 10, 12 against a 2 or 3, 13 against a 2, and the doubles of 9 against a 2, 10 against a 10 and 11 against an ace.

Why a handful of plays is worth so much

How much a deviation earns depends on three things: how often the hand occurs, how often the count is past the index when it does, and how much money is on the table at that moment. That last factor explains the ranking.

Insurance

Insurance is a side bet that the dealer's hole card is a ten, paying 2:1. It breaks even when exactly one third of the unseen cards are tens. Off the top of a six-deck shoe the fraction is under 31%, and the bet carries a house edge of over 7%. At a Hi-Lo true count of +3 the fraction crosses one third and the bet turns profitable. It tops the list because it comes up whenever the dealer shows an ace and — by definition — when the count is high, which is exactly when your largest bets are out.

16 against a 10

This is the closest decision in basic strategy: hitting is only marginally better than standing. The slightest surplus of tens tips it, which is why the index is zero. It is also one of the most frequent stiff hands. A shortcut many players use: stand if the running count is positive, hit if it is negative.

Splitting tens

At +4 or +5 against a 5 or 6, splitting a pair of tens is mathematically correct. It is also the single most recognizable card counter play there is, since no basic strategy player ever does it. Many counters deliberately skip these two for that reason. It is a judgment about attention, not about the math.

The negative indexes

Plays 14 to 18 apply when the count is below zero, when you should already be betting the minimum or not playing. They save a little on small bets, which is why they rank last.

The Fab 4 surrenders

If the game offers late surrender, four more plays are worth learning. In each case basic strategy plays the hand, and you surrender instead at the index or above:

Surrender is worth more to a counter than to a basic strategy player, for the same reason as insurance: the hands that get surrendered at high counts carry big bets.

How much do deviations actually add?

Less than beginners hope, especially in shoe games. In a six- or eight-deck game, the great majority of a counter's advantage comes from bet variation; playing deviations add a smaller share on top. In single- and double-deck games, where the count swings further and more often, they matter considerably more.

The practical consequence is an order of priorities: perfect basic strategy, an accurate count, a correct true count, a sensible bet ramp — and only then index plays. A wrong index applied confidently is worse than basic strategy.

A learning order

1. Insurance at +3. One number, the most valuable play.
2. 16 vs. 10 at 0, and 15 vs. 10 at +4. Frequent and easy to remember.
3. 12 vs. 3 at +2 and 12 vs. 2 at +3. "Twelve against a small card: stand when the count is high."
4. The doubles: 11 vs. A and 9 vs. 2 at +1; 10 vs. 10 and 10 vs. A at +4; 9 vs. 7 at +3.
5. The negative plays, if you ever play through bad counts.
6. The Fab 4, if your game has surrender.

Flash cards work well: the hand on one side, the index on the other. Then play the simulator in training mode, where a note appears whenever one of the supported deviations applies at the current true count.

Deviations with other systems

Index numbers belong to a specific counting system. The numbers above are for Hi-Lo; a level-two count such as Zen or Omega II has its own, larger indexes for the same plays. Unbalanced systems such as KO express the most important ones as fixed running counts instead — insurance at +3, for example. Never mix indexes from one system with the count from another.

Sources and further reading

• Don Schlesinger, Blackjack Attack: Playing the Pros' Way (RGE Publishing) — origin of the "Illustrious 18".
• Stanford Wong, Professional Blackjack (Pi Yee Press).
• Wizard of Odds — Introduction to the High-Low Card Counting Strategy
• Peter A. Griffin, The Theory of Blackjack (Huntington Press).