Folding Sit Pad
This is the lightest closed cell sit pad I could find. Weighs only 17.75 grams (video below shows 18.25 and the rubber band is .5 grams) and unfolds to 15 inches x 11 inches x .19 inch. Best part is it folds down to just 7.5 inches x 5.75 inches. I like to keep it handy at night in case there is a cold spot in my hammock.