Improved Critical

Improved Critical (General)
Select one type of weapon that you are proficient with. You have learned to wield that weapon with such skill as to inflict devastating quantities of damage very frequently.
Prerequisite: Base attack bonus +8.
Benefit: When using the weapon you selected, your threat range is doubled.
Special: This feat can be gained multiple times. The effects do not stack. Each time you take the feat, it applies to a new weapon. A character who has seven or more levels of thebarbarian class may not select this feat. If a character with this feat ever gains seven or more levels in the barbarian class, he immediately and permanently loses this feat.

Improved Critical

Glimpses of Hyboria Elfbane