The Stance is all business with ABS/Polycarbonate shell construction, 7-position shield system, and Dual-Density Styrene liner. The Stance exceeds all SNELL and DOT standards and features our plush, moisture wicking liner for a comfortable, secure fit. We have also incorporated a fully adjustable venting system to keep things cool on those long rides. Z1R Helmet Sizing Chart AdultXSSMLXLXXLHat6 5/8 – 6 3/46 7/8 – 77 1/8 – 7 1/47 3/8 – 7 1/27 5/8 – 7 3/47 7/8 -8Inches21 1/421 5/822 3/823 1/823 1/224 1/4Metric53 – 5455 – 5657 – 5859 – 6061 – 6263 – 64 YouthSMLXLAges5-66-88-1010-12Hat6 1/8 – 6 1/46 3/8 – 6 1/26 5/8 – 6 3/46 7/8 – 7Inches20 5/821 1/821 1/421 5/8Metric5-66-88-1010-12