1. If you have a measuring tape, measure from the right side of your face, where your ear meets your cheekbone, and measure to the left side, where your ear meets your cheekbone. Make sure to keep the tape measure snug around your nose. If this length is less than 10", we suggest the XS/S size. If this length is over 10", we suggest the M/L size.
2. If you don't have a measuring tape, you can use your weight to measure. Note this is the less accurate option. If you weigh less than 150 lbs, we suggest the XS/S size. If you weigh over 150 lbs, we suggest the M/L size.
If you are still uncertain of which size to use, we believe the M/L size will fit the majority of users. If the size ordered doesn't fit, please wash it, pack it up, and give it to a friend or neighbor.