This crew-neck has smart insulation. On the lower back and lower sleeves, water-resistant Nylon is used to beef up the areas you'll want protection the most. That, plus added thumb holes and discrete zippered hand pockets take this fleece to a pro level.
Synthetic insulation is measured in grams, so a jacket with a 80g rating simply means that a 1 meter by 1 meter piece of that particular jacket's insulation weighs 80 grams. The higher the rating, the warmer the outerwear.