Shop Klean Kanteen 27oz Kanteen Classic w Loop Cap. Our most popular size, the 27oz Kanteen® Classic is perfect for your on-the-go life. Whether you’re trying to juggle a full day of classes or work, or a trip to the dog park between your workout and happy hour, just one or two fill-ups will help you stay hydrated and happy all day. The 27oz is available with the Sport Cap 3.0; featuring a soft silicone spout, 25% higher flow rate and “chirp“ free hydration. Easy drinking and no whistling sound!