This is a fantastic sturdy lightweight flask the same one military pilots carry. It is flat and form fitting so that it is not too bulky when your vest or jacket are closed, yet has enough volume to be useful. It is made of plastic, so if you fall it will give and not break a rib like harder metal or plastic flasks. It seals nicely and is great for any liquid! THIS IS A VERY LIGHTWEIGHT MOLDED BPA FREE PLASTIC FLASK not made of metal. If you are looking for lightweight, sturdy with a good size capacity, this is the flask for you.