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The REI Midweight Polartec(R) Power Dry(R) long underwear bottoms offer you incredible value and excellent comfort. Polartec Power Dry use different yarns on each side of the fabric to enhance comfort: interior yarn wicks moisture, and exterior yarn dries quickly. The combination of the 2 yarns helps keep you dry during highly aerobic activities because it moves moisture away from skin faster than single-component fabrics such as cotton. 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. Fabric offers UPF rating of 30 to protect against harmful UV light. Closeout.