|Benefit||-1 roll on head(for example we have 5 tiers of critical if you roll tier 2 it will be counted as tier 1)|
|Penalty||-2 to Intelligence|
A thicker than average cranium means you can shrug off hits to the head that would floor others. Unfortunately that doesn't leave much room up there.
Note: Man of Steel does the same thing, but for all incoming damage and so the effects of both will stack for -2 to enemy's crit tier when head or eyes are hit.