The Easton S9 helmet is very similar in styling to the Easton S17 helmet, but it is equipped with a VN liner. A traditional liner that is popular for its low-profile fit. Dual density Vinyl Nitrile(VN) liner for comfortable, low-profile fit Single screw size adjustment Height adjustment earpieces can be easily adjusted higher or lower to your preferred height Superior ventilation - Easton has optimized the size and location of vents for an aggressive look and optimal airflow through honeycomb ventilation CSA, HECC, CE approved Fitting information: helmet size - hat size / circumference XS - 6 3/8-6 3/4 / 20 1/8-21 1/4" Small - 6 5/8 - 7 / 20 7/8-22" Medium - 6 7/8-7 1/4 / 21 5/8-22 3/4" Large - 7 1/8-7 1/2 / 22 3/8-23 1/2" XL - 7 3/8-7 3/4 / 23 1/8-24 1/4"