Designed to be worn alone, or under a helmet. 100% waterproof & good coverage to ensure you are kept warm & dry in all wear in all weather conditions. The Sealskinz Windproof All Weather Skull Cap in Black is a cap made for comfort and warmth. A lightweight three-layer windproof skull cap is... Close fitting - to be worn under protective headgear. Lightweight. Breathable Micro-fleece lining. Covers ears with perforations to aid hearing. Aqua Dynamic Design. Thermal rating: 2 - lightweight protection. Materials: 90% polyester / 10% PU.