[Carlos69]

It gives you the ability to adjust the amount of front braking by altering the amount of friction between the nylon washer and a face of the one way bearing... run it too loose and you get little or no brakes on the front wheels or too tight and you effectively lock out the oneway (and it's benifits)
Setting my FAB (had it for over a year now) is the final adjustment before I race as it has such a large role in how my car turns in, it just makes the car feel so well balanced - I'd never consider running without it.