What's the bag behind the swat vest?

The bag at the back of the special police vest is a water bag inside the back of the vest, which can hold three liters of water to quench thirst in an emergency. Special police combat vest, also known as special police tactical vest, combat vest, combat vest, etc. , specially designed for public security special police, equipped with a fully modular management tactical package, which can be randomly combined according to its own needs, and has passed the wear test for police officers to use in handling emergencies.