HydroLock lever on tube provides one-hand positive on / off even for soldiers wearing gloves HydroGuard: Embedded silver-ion technology inhibits the growth of bacteria on the reservoir and drink tube surfaces, making system easier to clean. (Does not protect the user from bacteria or other disease-causing organisms.) Cover protects drink tube from abraision and UV rays. Radio-Frequency-welded polyurethane reservoir is exceptionally tough and elastic even under heavy loads. Big Bite Valve: Made of self-sealing silicone, the single-piece Big Bite Valve supplies unmatched water flow with ease.