Kriega Hydrapak Shape-Shift™ Reservoir 3.75 Litre

Kriega says:

The Kriega HydraPak heavy duty, military grade reservoir and insulated drink tube is compatible with Kriega Trail9 and Kriega Trail18 Adventure Backpacks.

The 'First Wave' (military spec.) reservoir is designed for extreme environments. The 0.4mm thick Thermo Polyurethane (TPU) is twice the thickness of the standard consumer model. Fully reversible for easy cleaning / drying. A Wide Slide-Seal™ top makes it easy to fill and creates a leak-proof seal. The Hydrofusion™ tube is durable and lightweight with built-in foam insulation, this simple, but breakthrough tube helps keep your water cooler in even the hottest temperatures.

Surge™ Bite Valve naturally ergonomic design with twist on/off function and protective cover.

Plug-N-Play™ connect system lets you easily disconnect the drink tube (an auto shutoff valve prevents leaking) and remove the reservoir from your pack for convenient refilling while leaving the drink tube in position.