The Columbia Midweight Stretch Long Sleeve Top is a highly versatile base layer that’s perfect as an undershirt in the winter or a standalone shirt in the spring or fall. This long sleeve shirt features Omni-Heat™ thermal lining that’s designed to reflect and hold in heat while its Omni-Wick™ technology wicks away perspiration to keep you dry and comfortable. The body forming fit, ergonomic seaming, flatlock construction and 4-way stretch all help keep you moving while its antimicrobial treatment prevents bacterial growth.