Our Pre-2023 reservoirs come with a small plastic clip that can be used to hang from the slider top to the inside of a pack if that pack has a way of attaching it (such as a sewn in loop). This is known as a Nifco Clip. 

While the clip isn't essential to the operation of the reservoir, it will keep it upright and aid the flow of water. Please keep in mind that not all packs will have hanging options.