Patented side impact protection (PSIP) research-based mandible protection helps reduce the forces from side impacts. Technology feature consists of side shell extensions combined with side liner extensions custom inflation and an over liner for proper fit, comfort and stability custom-fit liner -premium inflatable liner components used to make final sizing adjustments to make a custom fit inflatable jaw pads to make adjustments for a custom fit Over liner - removable, moisture-resistant liner cover with properties built-in to protect the product, provides comfort and stability for patent information, visit Riddell/patents RIDDELL speed youth helmet size chart: s: hat size up to 6-1/2"; circumference = up to 20-3/8" m: hat size 6-1/2" - 7"; circumference 20-3/8" - 22" l: hat size 7" - 7-1/2"; circumference 22" - 23-1/2" xl: hat size 7-1/2" and up; circumference 23-1/2" and up if in between sizes, choose the smaller size RIDDELL fitting guide: a properly fitted helmet is an important first step in player protection to determine head size, wrap a cloth measuring tape around the circumference of the player's head measure approximately 1" above the player's eyebrows. Record measurement and refer to chart below if measurement falls between helmet sizes, choose the smaller size due to varying head sizes, the chart below is only a recommendation.