Needs review
Source: Player's Handbook

Description: You are an expert in fighting two-handed.

Prerequisites: DEX 17, Two-Weapon Fighting, Base Attack Bonus +9

Required for: Greater Two-Weapon Fighting

In addition to the standard single extra attack you get with an off-hand weapon, you get a second attack with the off-hand weapon, albeit at a -5 penalty.

Special

A 6th-level ranger who has chosen the two-weapon combat style is treated as having Improved Two-Weapon Fighting, even if he does not the prerequisites for it, but only he is when wearing light armor or no armor.