The Atom SL is designed to handle subtle climate shifts. Balancing air permeability with wind resistance, the shell material allows airflow during active periods, but helps cut the chill during static moments. 40g/m² Coreloft™ Compact insulation is highly compressible, insulates if wet, and delivers its superior performance for very little weight. All the Atom SL’s fabrics are selected to manage moisture and provide comfort while on the move. Sleeves are lined with a comfortable mesh, and lightweight fleece side panels help provide thermal performance and ventilation. Articulated sleeves and gusseted underarms extend freedom of movement.