Accepts Radioactive V audio system (sold separately). Ear pieces and liner can be removed for insulation adjustment and washing. Fleece chin strap cover protects you from irritation. In search of a comfortable helmet? The Boeri Siren comes in five sizes and boasts an adjustable fit dial. Getting a comfy fit was never so easy. Nine passive chimney vents keep just enough cool air coming in and hot air moving out to keep you pleasantly warm and dry. Pony Port eliminates fussing with hair ties, rubber bands and braids by providing a soft, simple way to keep your hair at bay. Removable plug system lets you close off the vents on especially cold days or open them wide for spring skiing.