Bonus armor

Bonus armor is a secondary stat that increases armor and attack power for tanking specializations. It can be found on rings, trinkets, necklaces, and cloaks.

Prior to Warlords of Draenor, bonus armor referred to extra armor on any cloth, leather, mail, or plate items, or any armor that was on any other type of item, i.e. trinkets, rings, and necklaces. This was indicated by the armor stat number appearing in green instead of the normal white.