Being able to withstand a barrage of strikes from some of the most dangerous practitioners on the planet is an art in itself.
It helps separate the pretenders who get put to sleep on a yearly basis from the guys who are nearly impossible to put away.
Now, while being naturally wired to absorb damage to the head like a sponge soaking up water isn't necessarily a developed skill set, it's highly beneficial.
So in anticipation of UFC 157, in which Dan Henderson's infamously indestructible chin will once again grace the Octagon, here are 20 fighters who have never been knocked out.
* There may be a few names left off this list, but without getting carried away, these are the most relevant fighters out there.