CNOC Hydriam Collapsible Bottle 750ml 42mm

The CNOC Hydriam 750ml is a collapsible TPU soft flask weighing 36 g, shaped with a tapered base specifically so it fits into running-vest and backpack shoulder-strap pockets rather than just the main compartment - narrower gear that most collapsible bottles designed for a pack's side pocket do not fit. Its 42 mm neck is compatible with Katadyn filters, so it can double as a filter reservoir at camp as well as a drinking bottle on the move. Being food-grade, BPA/BPS-free TPU, it packs flat once empty, though the tradeoff of collapsible soft flasks generally applies here too - they are less puncture-resistant than rigid bottles and need reasonably careful packing near sharp gear.