The Arc'teryx Women's Rho LT Base Layer Top is a top-rated choice for women's outdoor base layer tops. It is made with a blend of polyester and elastane, providing a comfortable and stretchy fit. The fabric is designed to wick away moisture and keep you dry during intense activities. The top also features a zip neck design for easy temperature regulation and flatlock seams for added comfort. With its lightweight and breathable construction, this base layer top is perfect for high-intensity outdoor activities.