A design that is truly successful. Nalgene in my opinion is the greatest style of water bottles in the world and I use it more than anything else. The size is tremendous. Whether it’s the Silo or the Classic bottle, both provide a good quantity of water. I have never had trouble with leaks and the bottles I have owned have lasted years without need for replacement. The replaceable cap is crazy useful and the strap that connects it easily allows you to hang your bottle on the strap of your backpack. Brilliant.