The hydrapak stash collapsible bottle has been designed to keep you hydrated without weighing you down this compact flexible and light weight water bottle packs down to an incredibly small and stackable size when not in use perfect for when you don39t need unnecessary weight or bulk in your backpack simply remove the cap and squeeze to pop open and twist n click to close the narrower mouth of the 750ml of the hydrapak stash bottle is easier to drink and pour from minimising spills