Note: Most (quality) helmets have different shell sizes, so each shell size will need its own template. To find out what size correlates to what size shell, you should contact the helmet manufacturer. If you find other templates online that say 'will fit all sizes'; that is not the case! If it doesn't mention a shell size it's better to leave it alone as well. In most cases, XS/S has a shell size, M/L has a shell size and XL/XXL.