You have mastered the art of defense in combat.
Prerequisites: Int 13, Combat Expertise, base attack bonus +6.
Benefit: When you use the Combat Expertise feat to improve your Armor Class, the number you subtract from your attack roll and add to your AC can be any number that does not exceed your base attack bonus.
Normal: With Combat Expertise, the number can be no greater than +5.
Special: A fighter may select Improved Combat Expertise as one of his fighter bonus feats.
Source: Complete Warrior, page 100.