Here's what other sites are saying:
Whether hiking, skiing, snowshoeing, mountaineering or Nordic skiing, REI Heavyweight Polartec(R) Power Dry(R) long underwear bottoms for women offer proven value in a warm, comfortable fabric. Polartec Power Dry utilizes 2 different yarns on either side of the fabric to enhance comfort: interior yarn wicks moisture, and exterior yarn dries quickly. Combination of the 2 yarns helps keep you dry during highly aerobic activities because it moves moisture away from skin and dries more quickly single-component fabrics. Fabric offers UPF rating of 50+ to protect against harmful UV light. Women-specific fabric is slightly heavier relative to men's fabrics and offers additional insulation. Smooth surface of outer fabric makes it easy to put on additional layers. Flatseam construction is soft and non-chafing next to skin. Brushed elastic waistband ensures a comfortable fit outing after outing. Next-to-skin fit hugs the body, maintaining skin contact to boost fabric performance.