Comes standard with CamelBak's NEW Water Beast™ durable material, leak-proof screw-cap and Big Bite™ Valve. Includes HydroGuard Anti-Microbial Technology. CamelBak's Reservoir's are made of an incredible polyurethane material that is 1.6mm thick! It can withstand near boiling water and can actually be frozen solid with water inside. That means it will not burst - so you can be as tough on it as you want without worry.