the 21/22 fw women's source powerair crew is a mid-layer for cross-training and layering through deep winter. polartec® power airâ„¢ fabric is the perfect foundation for a high-performance crewneck that insulates against the cold — it's warm, wicking, and also sustainably made. with a sleek cut and set-in sleeves, this crewneck moves as you do thanks to 4-way stretch.