Thanks to the smaller opening of the Narrow Mouth less water can rush out, making it easier to chug mindlessly. Everything else about the Narrow Mouth is like its Wide Mouth compatriot, so you get all the durability and no-leak peace of mind but without the stress of a mess. Just note that no ice cubes or lemon wedges are getting in here, so if you prefer more than water in your water bottle, check out our Wide Mouth bottles.