Water is a very important resource, especially in a campaign or on the battlefield, which you need to have with you, at least in a half-liter flask, but the experience of the war in the desert was the reason for the creation of "hydrators" that fit perfectly into the equipment of a modern infantryman.   

A hydrator is a drinking system, a silicone flask with a drinking hose. The size of the flask is 1.5 liters 170×350 mm.

Designed for use with backpacks that have elements for placing drinking systems.