Built for cool-weather runs and post-activity warmth, the Smartloft is our top pick for women who want insulation without bulk. Merino wool fill delivers natural temperature regulation and odor resistance, so it stays fresh across back-to-back wears. The relaxed-but-not-sloppy regular fit layers easily over base layers or under a shell.

• Merino wool insulation provides natural warmth that regulates with your body temperature — not just trapping heat
• Wool fill resists odor better than synthetic insulation, making it a smart pick for multi-day trips or travel
• Regular fit is cut to layer comfortably over a long-sleeve base without restricting arm movement
• Works as a standalone piece in cool, dry conditions or as a mid-layer when temps really drop
• Available in Twilight Blue — a versatile, low-key colorway that transitions from trail to town