They add 75 horsepower and help the suspension flex while making it easier to change your oil.
Na, I'm kidding. They keep you from crashing up your front end. Thats what any big steel bar outside the bumper does. They are just special made for severe off road conditions, like end over end flip prevention and rock skidding, as mentioned above and in the other thread.
Meaning no offense, but if ya have to ask, I doubt your wheeling habits require them.
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