Fit, feel, and functionality are all a big deal when wearing a mask for a full day of sun and wind protection.
Shirts:  Bust/Chest. Measure around largest part of chest with measuring tape around shoulder blades and under arms.  Sleeves. Bend elbow and measure from the center back neck, around the shoulder, past elbow, to the wrist. Note: All long sleeve shirts feature a button tab that allows it to double as a rolled-up short sleeve.  Neck. At the narrow-most part of the neck, measure around the circumference.
Pants:  Waist. Measure around the waistline with a loose tape. Round to the next size up. Note: All waistbands have elastic in the rear of pant that provides a flexible, comfortable fit.  Seat. Measured 8" below the top of the waistband.  Inseam (Voyager Pants). Measured from crotch to leg opening.  Rise. Measured from crotch to top of the rear waistband.
Headwear:  Measure circumference across the forehead (above brow) above the ears to the back. For all headwear, one size fits all from hat sizes:
6 1/2 (20.5" [or] 52cm) to 7 7/8 (24.625" [or] 63cm)
Select the size range that fits your actual measurements.
Headwear (Left) and Face Mask Tube (Right) Size Chart
Aqua Design | Men
Aqua Design | Women