Heat Holders® Men's ORIGINAL™ Base Layer Zip Top is a heavy weight thermal base layer ideal for extreme cold. DUAL BRUSHING Supersoft HeatWeaver® yarn is carefully brushed both inside and out to maximize warmth and softness. PERFECT STRETCH Our knitting technology and attention to detail produce the perfect stretch for freedom of movement and fit. FLAT COMFORT SEAMS Our carefully finished flat seams minimize bulk to create a comfortable non-chafe fit, perfect for layering. MOISTURE & ODOR MANAGEMENT Moisture and odor management technology helps keep you drier, fresher and more comfortable. 1/4 ZIP TOP Quarter Zip provides great control for thermoregulation and prevention from overheating. Great for layering and adjusting to varying temperatures throughout the day. Matching Bottoms also available.