I'm 5' 10" and typically have a hard time finding the right size shirt. I wear what I would consider a Marge. I need a large medium or a small large. My wife bought this hoodie for me and bought it in a size medium. It is a great fit. My suggestion would be that if you can't decide what size to get, buy the smaller one. The hoodie is very warm, and is very similar to Under Armour's Cold Gear tights. The exterior is rather slick while the inside has the fleece lining. The wind will cut through the material, so don't expect it to keep you roasty toasty on a windy COLD day with nothing but a t-shirt under it. However, it is very comfortable, great fit, and will keep you warm. This is a great product.