Many accessories are available for Klean Kanteens. All caps and lids are interchangable with all sizes of Klean Kanteens and we only use non-leaching Polypropylene #5 (PP#5) in our caps and lids. Both the loop and flat caps have stainless steel bases to prevent plastic from coming in contact with your beverage.
Customer Rating: 
Summary: excellent
Comment: I ordered the 18 oz. canteen first. Then I ordered the sports cap. I love it! The cap does not leak. I feel like I am doing something good for the environment when I drink from my "Kleen Kanteen." I will never buy bottled water again.
Customer Rating: Summary: user friendly sports cap
Comment: After ordering the Klean Kanteen 40oz I used it w/
its original top. Then I ordered the sports cap,
and what a difference. No leaking, easy to drink from,
convenient. I love it, and ordered one for each person
I am giving the Kanteen to. Get it!
Customer Rating: 
Summary: Solid cap, doesn't whistle if you use it right.
Comment: Its a solid sports cap that is designed specifically for KK. The reason it whistles is that the Kanteen is solid steel and unlike plastic bottles you cannot squeeze it to get the water out. You actually have to suck on the cap to get the water out. There is actually a little soft plastic valve that opens when theres negative pressure in the bottle letting air in from the outside. This is what causes the whistling. If you orient the cap so that this valve is on top and not touching the water inside, it wont make that chirping noise. A bit annoying (thus the -1 star) but it isnt something that is a real dealbreaker.
Customer Rating: Summary: Good...but noisy.
Comment: We love that there is a sport top for our Klean Kanteens, but they are so noisy to drink out of! It sounds like a bird is whistling, if possible. My boys can't bring them to class because they disrupt the teacher. Other than that, they fit nicely and allow you a good flow.
Customer Rating: Summary: Not perfect but okay
Comment: There are two major problems with the sports cap: (1) it leaks a little, and (2) it makes a really bizarre chirping noise when I use it. People have asked if it was designed to also attract birds. The chirping is fine outdoors but not so great when I take my Klean Kanteen to class, but the leaking is really annoying if you tend to throw your water in your backpack or on the floor of your car. It isn't a huge leak (you won't have a puddle anywhere) but there will be enough water collected on the lid that it might drop onto you when you try to take a drink. Annoying.
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