The '"Pack Sack" is an awesome optional addition to the Becker Patrol Pack and Becker Raider Pack! It offers great versatility and functionality - highly useful! It quickly attaches/detaches via our custom-made clips and bungee cord. Designed to hold an outer layer or poncho or poncho liner or wet stuff you don't want on the inside of the pack, but we find ourselves using it as a catch-all "stuff sack" for all kinds of things. The design allows full access to the front pockets of the Patrol Pack as well as the lower zippered pouch of the Raider while also allowing utilization of the front pocket pass-throughs. We knew it was good but until we took it out into the field for harsh environment testing, we didn't fully realize just how useful and valuable it is!