We're working out what we think - we'll add our view here!
Hydrapak says:
Fill. Drink. Pack. Repeat. With durable construction and minimal design for easy packing, the flexible Stow™ 500ml helps make all your adventures the best they can be. Add the flip top cap with spill-proof valve for easy drinking, bail handle for comfortable carrying and attachment, and a weight 80% lighter than most hard bottles, and you’ve got a perfectly pocketable bottle.
We're working out what we think about Hydrapak's 2021 Stow Bottle 500ml, we'll add our comments here in due course.