Similar to a regular waist bags, an army waist bag is used to hold miscellaneous essentials that you need during a mission. Also, it has specialized attachments to hold it to the tactical belt.
While having adequate size and durability is important, it is essential for a military waist bag to have a secure attachment point that will not rip or flap around when running.
These bags are usually very important. In such a pouch you can keep documents, certification, as well as minor tools that may make your job much easier.