evo.com | Smartwool Long Underwear Tops > Smartwool's new Intraknit base layer construction was a smash last winter, and they continue to pile it on this year. The Smartwool Intraknit Thermal Merino Base Layer 1/4 Zip Top combines Merino wool with polyester for fast dry times, cozy warmth, and enhanced durability in the mountains. 53% Merino Wool / 45% Polyester / 2% Elastane Slim Fit Ribbed Elbows 3D Mapping Results in Near Custom Fit Mesh Ventilation | Smartwool Intraknit Base Layer 1/4 Zip Top Men's 2025 - X-Large Green | Wool/Elastane/Polyester