~Adidas Terrex says~ 

A lightweight, packable and insulated jacket.

A packable, portable jacket with lightweight PrimaLoft® insulation for comfort in all conditions. A water-repellent outer material protects in light rain, and premium insulation retains warmth even in wet conditions. This jacket layers easily, making it the ideal companion no matter what the day has in store. Wear over a t-shirt in place of a sweater, or layer under a waterproof outer shell for added protection. This durable, versatile jacket is a wardrobe essential that packs down easily into its own pocket for storage. Whatever your summit, you're good to go.