From the manufacturer

Men's UA Base 4.0 Crew

UA Base 4.0 men's cold weather leggings are built for extreme cold weather and lower activity. Their unique pattern traps heat without adding bulk. Think long underwear, revamped for today's top athletes.

• UA Base 4.0 Extreme Baselayer is our warmest yet, delivering extreme warmth in the extreme cold
• Soft, brushed grid interior traps air against your skin, closely managing your body's microclimate to keep you warm & comfortable
• Material wicks sweat & dries really fast
• 4-way stretch material moves better in every direction
• Fitted: Streamlined fit that’s not too tight or too loose.