Measure the circumference of your head with a non-elastic tape measure. Place the end of the tape on your forehead and wrap it around the rest of your head, keeping it 1" (2.5 cm) above your ears. Hold the point where the tape meets the other end, lift the loop you have formed over the top of the head and record the measurement. Be as careful as you can to get the most accurate measurement possible.
| One size | A | B | C | D |
| INCHES | 20 ⅝ - 23 ⅝ | 4 ½ | 2 ½ | 7 |
| CM | 51-59 | 10 | 9 | 18 |
