I bought the Mountain Hardware compressor jacket as a synthetic down liner for another jacket (called the shell). The outer layer is waterproof, and you next the two together when you need something really warm. It was for a big hiking trip two years ago, but since then, I have work this "liner" so much, it's unbelievable. It's really thin, yet keeps you warm up to freezing. I can wear it from about Sept to Jan before I need to break out the outer shell, and it looks really cool. Not big and puffy, and pretty sleek being made of a nylon outer material. Highly recommended for anyone...read full review »