Detailed Explanation of CO Open-Range: How to Maximize Advantage in CO Position

STRATEGY article: co-open-range-guide-mqbizn8z (part 1/2)

Position Scenario Overview

[Cut Off] (CO, Cut Off) is the position to the right of the dealer (BTN), before the Button and after the Hijack (HJ) in the preflop action order. Because the CO has positional advantage postflop (only behind BTN) and can directly pressure players who fold to the Button, the CO's open-raising range is relatively wide but still needs adjustment based on opponents and game dynamics.

Recommended Range (Hand Types in Text)

In a standard 100BB deep six-handed game (6-max), the CO's open-raise range is typically about 20%-25% of hands. Specifically:

• Strong Hands (Value Raises): All pairs (22+), all suited aces (A2s+), ace-high offsuit (A9o+), suited kings (K9s+), king-high offsuit (KTo+), suited queens (Q9s+), queen-high offsuit (QTo+), suited jacks (J9s+), jack-high offsuit (JTo+), suited connectors (T9s, 98s, 87s, 76s), and some small suited gap hands (e.g., T8s, 97s, 86s).
• Marginal Hands (Mixed Strategy): Some offsuit aces (e.g., A8o-A2o) can occasionally be raised but cautiously; small suited connectors (65s, 54s) and some suited gap hands (e.g., 75s, 64s) can also be range extensions.
• Folds: Low offsuit cards (e.g., Q9o, J9o, below T8o), offsuit connectors (e.g., T9o, 98o), and all offsuit junk hands.

Note: The above is the standard full range. In practice, mix raises and limps based on opponents and table dynamics.

Range Construction Logic

CO range construction is based on the following principles:

1. Positional Value: CO has postflop positional advantage over the blinds and the Hijack (if HJ limps), allowing more frequent opens compared to early positions. However, compared to BTN, CO still faces a potential 3-bet from the Button, so the open range is slightly tighter than BTN.
2. Pot Odds & Pressure: CO's raise (usually 2.5-3BB) directly forces folds from HJ and earlier positions while putting pressure on the blinds. Suited hands and connectors in the range improve postflop playability.
3. Balance: The range includes both strong value hands (big pairs, AK, etc.) and speculative hands (small-medium pairs, suited connectors) to protect strong hands against frequent 3-bets from opponents.

Adjustment Factors

CO range must be dynamically adjusted based on:

• Button Style: If the Button player is aggressive (high 3-bet rate), tighten the CO open range, especially marginal suited connectors and weak aces. If passive, widen the range.
• Blind Tendencies: If blinds frequently defend or 3-bet, reduce speculative hands and increase value hands. If blinds fold a lot, widen the range to about 30% of hands.
• Stack Depth: At shallow stacks (<40BB), speculative hands lose value; focus on high pairs and high cards. At deep stacks (>150BB), suited connectors and small-medium pairs can be raised more often.
• Number of Players: At a full-ring table (9 players), the CO open range should be tighter than 6-max (about 17-20%) due to more players behind.
• Game Dynamics: If multiple players limp, tighten the CO raise range significantly and prefer large raises with strong hands to isolate.

GTO Reference

According to modern GTO solvers (e.g., PioSolver) for 6-max, 100BB depth:

• Standard CO Raise Range: About 22-23% of hands, including all pairs (22+), A2s+, A9o+ (sometimes A8o-A7o), K9s+, KTo+, Q9s+, QTo+, J9s+, JTo+, T9s, 98s, 87s, 76s, and some T8s, 97s, 86s, 75s, 65s.
• Mixed Strategy: Small ace-high hands like A2o-A5o, A2s-A5s sometimes mix raises and folds depending on opponent frequencies.
• 3-Bet Response: Facing a 3-bet from BTN or blinds, CO should 4-bet about 3-4% of range (e.g., QQ+, AK, and some suited connectors as bluffs) and call with about 15-18% (e.g., small-medium pairs, suited connectors, ATs, etc.).

Note: GTO ranges are baselines; adjust in practice based on opponent deviations.

Practical Application

1. Leverage Position to Isolate: When the HJ limps, the CO can raise with a wider range to isolate, especially with speculative hands. The raise size is typically 3BB + 1BB per limper.
2. Responding to 3-bets: When facing a 3-bet from the button, the CO's calling range should favor suited connectors and small-to-medium pairs, as these hands better utilize postflop position; fold weak offsuit aces (e.g., ATo, AJo) to avoid being dominated.
3. Blind Stealing: If the blinds fold to steals at a high rate (fold to steal >70%), the CO can raise with roughly 28-30% of hands, including all suited connectors and some offsuit K-high hands.
4. Range Notation: In practice, it is recommended to use a default 20% range in the CO and adjust based on opponents. Start conservatively and gradually widen the range once comfortable.

Examples:

• Typical Scenario: 6-handed, 100BB effective stacks, all opponents tight-passive. The CO can raise to 2.5BB with 76s (suited connector) and play flexibly on the flop.
• Adjustment Scenario: If the button has a 3-bet frequency as high as 12%, the CO should fold marginal hands like T9s, K9s, and only raise with strong hands.

Remember: The CO is a profitable position, but opening too wide can be exploited. Learn to balance value and bluffs, and leverage positional advantage to achieve long-term profitability.