Improved Back to Back

Teamwork

After much practice, you and an ally have become adept at fighting in close proximity to one another.


Prerequisite: Back to Back, Perception 5 ranks.


Benefit: While you are adjacent to an ally who is flanked and also has this feat, you can spend a swift action to gain a +2 bonus to AC against all flankers until the start of your next turn.


Source: Ultimate Combat