Replace your S1 Lifer Helmet Sizing Liners with some fresh ones! The S1 Lifer Helmet Sizing Liners are replacement front and back pads for the S1 Lifer helmet. These Liners are compatible with both our regular Lifer and Mini Lifer helmets. Sizing for Regular Lifers works as such: Small (Red) fits 21" heads, Medium (Gold) fits 21.5" heads, Large (Black) fits 22" heads, X-Large (Bright Green) fits 22.5" heads, XX-Large (Blue) fits 23" heads and XXX-Large (Purple) fits 23.5" heads. Sizing for the Mini Lifers works like this: X-Small (Grey) fits 18.5" heads, Small (Red) fits 19" heads, Medium (Gold) fits 19.5" heads, Large (Black) fits 20" heads, X-Large (Bright Green) fits 20.5" heads. If you are confused just give us a call and we will help you out.