ACU Patrol Cap Fitting Guide
The DA PAM 670-1 4-10a(2) specifies how the ACU Patrol Cap should be worn:
The patrol cap will fit snugly and comfortably around the largest part of the head without bulging or distortion from the intended shape of the headgear and without excessive gaps.
Reference the Sizing Charts below when choosing your size. If you don't know your measurements, reference the image below the charts for how to get your measurements.