Improved Low Blow

Combat

You are adept at hitting larger opponents where it hurts.

Prerequisite: Base attack bonus +4, halfling, low-blow racial trait.

Benefit: Your bonus to confirm critical hits against opponents larger than yourself improves to +2. Furthermore, once per day, after you fail to hit with a critical hit confirmation roll, you can reroll the confirmation roll, but must take the new result even if it is worse.

Source: Advanced Race Guide