Triple Eight Pro Model Helmet Sizing Chart:

To ensure a perfect fit, measure the circumference of your head starting in the middle of your forehead and match it with the sizes below.

XSmall:  20.1”  – 20.5”

Small:     20.6" - 21.3"

Medium: 21.4” – 22.0”

Large:    22.1” – 22.9”