About Columbia Sportswear Omni-Heat® 3D Base Layer Top - Midweight, Long Sleeve (For Men)Closeout. Columbia Sportswear's base layer top offers Omni-Wick® and Omni-Heat® technologies to pull moisture away from the skin and offer midweight warmth for cold-weather layering.Omni-Heat® thermal-reflective lining reflects and retains body heat for an average of 20% more warmthOmni-Wick® advanced evaporation technology moves and disperses moisture away from the body for rapid evaporationFlatlock seams reduce chaffingAntimicrobial treatment reduces odor-causing bacteriaBase layer weight: Midweight