Husky 9416569 Air Compressor Regulator Knob Kit. Includes the knob, diaphragm, and internal parts (no manifold).
If air leaks from the regulator or if when you turn the knob it doesn't adjust the PSI up or down, replace this part.
Knob Repair Kit for Regulator
very quick delivery, part fit perfectly and my air compressor is back up and running.