The Columbia Women's Glacial IV Half Zip Fleece is a popular synthetic base layer top for women. Made from soft and cozy fleece fabric, it provides warmth and comfort in cold conditions. The half-zip design allows for easy ventilation and temperature control. This base layer top is highly rated for its versatility, as it can be worn as a standalone piece or layered under other clothing. It is also praised for its durability and stylish design.