The Eberlestock® Batwing Pouch is designed to function similarly to the tall, narrow pockets on their J-Type packs. They provide an excellent and very simple way to stay organized: because they don't have excess lateral space, things don’t move around as you go through your paces.
You can add a Batwing or two to just about any of Eberlestock's packs. Use two of them with the F1-Mainframe or M1 Carrier Frame to build a great minimalist day pack that will still be ready for any heavy pack-out. Or, add them to a J-type pack to add a third or fourth tube as a handy and simple way to increase capacity.