This women’s ThermoBall™ Active vest was designed for cool weather training and outdoor activities, wearing well as an outer layer over a sweater, and as a mid layer under a rain shell. Its hybrid construction pairs ThermoBall™ insulation throughout the vest core, with strategically placed grid-fleece stretch panels along the shoulders and sides. PrimaLoft® ThermoBall™ is a patented synthetic insulation that retains heat even when its wet by utilizing small synthetic-fibre clusters to deliver heat-trapping warmth, at a ratio similar to down filling. The shell covering the vest’ insulated core is made from durable ripstop nylon and has a water-repellent finish. The North Face furnished the interior with a FlashDry™ liner that wicks away any sweat and moisture that accumulates during activities.