i have had several people ask me about reg for the iwata guns . a gauge that has 20 lb jumps is pretty useless under 30 lbs. if your going to use an iwata buy the reg for it . it is much more accurate under 30 lbs. the iwata starts with 5 lb jumps.
Might add to this that many of the "regulators" for spray guns are not regulators, they are nothing more than a flow control. They do not belong on a spray gun. Spend the money and get a diaphragm regulator.
I finally figured out what the flow control thing is good for, a speed control on a die grinder.