Hands-free is an important quality for many pieces of tactical and operational equipment used by the military. One piece of hands-free operational equipment is a hydration system. Developed over 20 years ago by manufacturer CamelBak, a hydration system – or pack – was originally used for outdoor activities, such as bicycling, kayaking, or hiking. In the present, many packs have been developed by CamelBak and other manufacturers to fit the specific needs of the military.

The typical hydration system uses a backpack or waist pack design. A reservoir or "bladder" made from rubber or flexible plastic takes up most of the design, and this component usually holds between 1.5 and three liters. The reservoir has a capped mouth, which is use for filling the reservoir with liquid and attaching a hose. The hose end closest to the user is equipped with a bite value that allows the user to open the hose and access the liquid in the reservoir. This part may be protected by a dust cover.

Water inside a hydration system may need to stay cool or not freeze at points. Some hydration packs designed for athletes and the military are insulated to keep the water inside from freezing or from becoming warm – whichever is needed by the user.

Hydration packs in a military setting are worn by soldiers in the field, on vehicles, and in airframes. Because of this specific need, military hydration reservoirs are designed to accomodate.

The attachment mechanism is different when a hydration pack is used as operational equipment. The pack is designed to attach to body armor or a larger tactical pack in these cases. More specifically, one will attach to the back of an IOTV, MTV, or plate carrier. Shoulder straps are not needed and the pack won't move or sway side to side when attached to body armor.