The internal comfort foam (memory foam) liner, ensuring a constant thickness even over years of use. The liner is removable thanks to a much stronger clip system rather than the well known scratch/velcro system. It is machine washable and it's therefore possible to wear a fresh and clean helmet daily if needed. The extra liner gives you the freedom to change to a dry one, if you ride several horses a day, or if you want to have one to wear while you wash the other.