Replacing your liners or adjusting the fit of your S1 Lifer and Mini Lifer helmet is so easy with their helmet sizing liners. All liners are compatible with all the S1 helmet shell\'s and can be mixed and matched to find your perfect combination S1 Helmet Co are an independently owned and operated brand that is deeply rooted in the Californian skateboarding, longboarding, BMX and roller derby scenes. Today S1 Helmet Co has an extensive line of protective helmets that are rapidly becoming known throughout the industry, thanks to their unrelenting approach to style and safety. The S1 Lifer helmets offer up to 5 times more protection than regular soft foam skate helmets and offers a superior fit. Sizing Info: ColourSizeThickness Grey X-Small 14mm Red Small 12mm Gold Medium 10mm Black Large 8mm Green X-Large 6mm Blue XX-Large 4mm Purple XXX-Large 2mm