Most males = Large. Most Females = Medium
There is no hard rule for mask sizing. Most males with a good sized head wear the large; most females medium. That being said, If you are a male with a particularly narrow or small head, the medium may be a better choice. Same goes for females with large skulls; you may want a large. For more specific measurements, check out our Mask Sizing Chart.
Ensuring a good fit is the most important aspect of any mask.
As a rule of thumb mask sizing is as follows:
a. 5’ Light Build = Small
b. 5’ Heavy Build – 5’6’ Average Build = Medium
c. 5’6” Heavy Build – 6’ Average Build = Large
d. 6’ Heavy Build – 6’+ Average Build = X-Large