Backstabbing

A Backstabbing weapon excels at attacking creatures' weak spots. When the wielder is in a position to score a Sneak Attack, a Backstabbing weapon is more accurate and also deals additional points of damage against the foe, even if the wielder has no Rogue levels.

If dual wielding, the bonus granted by this trait applies to hits with either weapon. If both weapons have this trait, only the single highest bonus applies.

Rogue Sneak Attack feat bonus stacks with Backstabbing weapons (source).