I purchased another one on these RTA's from Fasttech. This time stainless steel instead of black. I should have ordered the black again. The AFC is much more free moving on the stainless one. I can't say that it's been an issue yet, but I just like the tighter feel of the AFC on the black one.
I have the SS version and when the tank is on my mod I can barely adjust the AFC...which is no problem since I keep it wide open all the time. But if I was wanting to adjust it I would almost need a sharp tool to move it or my fingernail. I don't have a black one, but if it is tighter than the SS I'm not sure it could be adjusted on the mod very easy at all. Maybe mine is just extra tight?