SUL down sweater .75 (custom size)
The SUL (super ultralight) series garments are aimed at pushing weight as low as possible for a given fill amount, without compromising function. They are down sweaters in the strictest sense. Like a knit sweater, no zippers, no pockets, no drawcords, no linings, no webbing, just insulation in the form of down in a nylon shell.
Fill type - 950fp DWR down
Fill weight - 1.6oz
Total weight - 3.8oz (small)
The goal with the SUL down sweater .75 was to make the lightest jacket possible that was still reasonably warm. This is about the lowest fill density that I felt could still maintain coverage without bunching and shifting too much inside a 4" wide chamber. It is surprisingly warm for such a light garment. I estimate this might go down to freezing while inactive, but it's probably getting uncomfortable for most people in the 30s (Fahrenheit).
A puffy is most often used as an inactive layer for stops, at camp, or to help boost a sleep system. They don't make for very good active layers since your sweat can easily compromise the down fill. This makes a zipper for ventilation a somewhat frivolous feature that can add a significant amount of weight and bulk. Pockets can be nice to have, but they often add a big chunk of weight and bulk and compromise the performance of a jacket by creating cold spots and by pulling insulation flat when there is weight in them. For those wanting pockets to warm hands I recommend adding a few inches to the sleeve to cover your hands. This is lighter than pockets and doesn't compromise the overall warmth. Drawcords can be good for cinching a jacket tight to your body to keep out drafts, but then again, the jacket could just be sized right to your body so we can leave off an ounce of cords. All non-essential sewn through lines have been eliminated so the down can loft and cold spots are reduced. Simplicity and reduced weight and bulk are not the only benefits of all this. Leaving off many tedious features also reduces my labor and allows me to offer a very affordable jacket at an extremely low weight.