The net result of this is that Monks have by far the highest AC without any armor on, or in light armor, but their highest armor values are lower than those of the other classes. His AC with mail on will be lower than his AC without any armor at all. High AC plate will still give the Monk his highest possible defense, but he’ll gain less defense from it than any other character class in the game, and he will usually suffers an AC penalty by wearing mail. The Monk has an odd property in that he gains less defensive benefit from heavier armor.