1.5 ounces! (small). These pants have a simple drawcord waist with the option for large cuffs so they can be put on without removing shoes or other layers. They are constructed from 1.0 oz Hyper D (uncalendared), which is a 20d fabric that has more breathability than the Argon Wind Shell options.
The functionality of an ultra light wind shell should not be understated. I have replaced many of my light/mid weight insulation layers with wind shell layers due to the shocking amount of warmth provided at such a low weight. Not only does it block wind and prevent evaporative and convective cooling, but it holds a pocket of warm air around your body that provides decent insulation. The Argon 90 wind shell layers provide a good balance of breathability to windproofness (40cfm) that is suited to lower levels of activity with great wind protection. HyperD is a large jump up in breathability that is much better suited to higher levels of activity while still maintaining good protection from wind. At 20mph you will start to feel some wind cutting through a bit, but it still stops a lot of it. While I don’t know the actual cfm rating of this fabric I would estimate it somewhere around double that of Argon 90 and it is much more comfortable when putting out a higher effort. It also has a very soft feel that is nice against the skin. These can double as cozy sleep layers. It also has a DWR coating that can shed some light rain.