I bought the follow rest sometime ago, I just now got around putting ball bearing fingers on it. Hopefully this will help maintain tolerances across the length when I turn AR barrels. The contour is just straight across the length, but before I was getting fat diameter in the middle, that was without follow rest. I tried the brass finger once, did not like them, maybe the ball bearings will be better.
One of these days I will convert the backside finger with a pneumatic pressure system. I figure a 2 inch pancake valve with 100-125 PSI should provide enough push. Pressure, as long as the air is regulated, should be constantly adjusted automatically as the diameter decreases.