A lot of protection for 4 oz.
A quality wind breaker provides a lot of warmth when water resistance is not paramount. The Patagonia Houdini makes taking a wind layer a no-brainer for mountain biking trips, 3 season hiking, light climbing, or just walking around town. You get an awful lot of versatility for just 4 oz. The caveat being that there are very few features outside of limited cinching areas in the hood and around the waist. If you do not need any extra features and you don't put it up against more than a drizzle, you will be very happy with this jacket.