The keyring bag weighs only 40g and comes with a stainless ring.
Its packaging is so tiny that you have no reason not to carry at least one with you at all times!
Mission bag with water-supply delivery system, light weight and easy to use, quick refill cap, external D-Links so it can be easily attached to a molle vest or rucksack, excess strap keepers, small external pouch for utilities with molle straps.