I bought this to use with my pressure gauge calibration set-up for calibrating the gauges at a brewery. My old regulator "drifted" far too much, making it very hard to calibrate a gauge. This one works quite well and is stable once you get it to a desired pressure. Ports are the right sizes and locations for my use. This is a relieving gauge, so if I overshoot my desired pressure it's just a matter of backing off a bit.
In the photo, the digital calibration gauge is to the right, gauge being calibrated left, on the regulator, and air in far left.