The Shrew seat bag is a low profile, roll top bag that fits pretty much any bike out there, dropper posts included. It utilizes the indie-rail straps, and has an integrated bottom support to prevent any sag or sway. It holds just the right amount of stuff (jacket, snacks) for a day ride.

Indie rail straps tighten to each saddle rail independently, resulting in greatly reduced sway

Compatible with most seat posts including dropper, suspension, aero, or high setback seat posts