You can control how much paint flows out of the gun by changing the size of the needle and fluid tip. This 1.4 tip size is good for topcoats, but larger tips, 2.0 or 2.5, flow more paint and are good for thicker materials, such as primer intended to go on in heavier coats. Smaller tips, like 1.3 and 1.0, are also available and are good for spraying clear, which can run or sag (or both) if sprayed on too heavily. Needles act like a drain stopper, blocking the flow of the paint and air. They are available in different sizes, too, and must match the fluid tip size you're using.