Shirt jackets — or "shackets" — are versatile pieces, working both as outerwear and as middle layers when temperatures dip. Outerknown's Origin Shacket is a solid example. It's crafted from recycled polyester and filled with synthetic insulation for lightweight warmth. The snap closure makes for easy layering, while a simple chest pocket and tonal stitching keep the appearance minimal. A pair of handwarmer pockets at the hip complete the low-key aesthetic.