The whole point of these products is to fine tune the air output of each outlet in order to set the function needed perfectly. For example, an air powered ornament needs a different amount of air than a bubble wall, than an under gravel filter, etc.This product fails this big time. It's impossible to fine tune anything because the knobs don't turn smoothly, if at all. I have to use pliers on them to get anything different from full on or full off and the sticky action of the valves makes even crude settings impossible.I would have been better off using a rats nest of tee's.