I recently found the best canteen I've seen on the market. Lifeline Smart Cap canteen sold at Sportsmans Warehouse stores and online. This canteen is shaped like the military's style and will fit into the stainless steel military cup and newer ACU canteen cover. If you empty this 32oz. canteen and you have the 3 piece set up that I have. Then you can boil water from a stream in the steel cup to sanitize the water.
The canteen, itself, is made from BPA free, tough plastic that is clear so you can see what you are cleaning. It also has a drinking spout and a wide mouth cap that is large enough for ice cubes. If you are looking for a great canteen, please give serious thought to the Lifeline Smart Cap Canteen.