Warm weather is never a constant, even in summer. Fog rolls in, a sudden thunderstorm blocks the sun, and changes in elevation and levels of exposure can cause temperatures to suddenly shift. But summer conditions seldom require bulky insulation. The Atom SL Hoody is specifically created to hit the zone where insulation is required, but in a measured amount that suits milder conditions. Providing warmth comparable to a lightweight fleece for significantly fewer grams, the Atom SL is an efficient midlayer in cool conditions and a great standalone during rest breaks, early morning starts, and while enjoying the view from a freshly bagged peak.