Lightweight Insulation

It’s designed to trap just enough heat during moderate activity or mild conditions. Think of it as your go-to midlayer for days when a heavy puffy is too much, but a baselayer alone isn’t enough.

Synthetic active insulation, like Octa or Coreloft, mimics fleece warmth but packs smaller and handles light moisture better. Fleece, especially grid fleece, breathes exceptionally well and feels great against the skin. For high-output climbs, many guides prefer grid fleece for its simplicity and temperature control.

Grid fleece uses a pattern of raised channels that trap warmth while allowing air to circulate. It’s lighter, more breathable, and faster-drying than traditional fleece — perfect for layering under a shell or wearing solo on dry, cool days.