The everyday OTF (on the fly) water bottle by Nalgene is an ultra-light water bottle of very high-quality construction. It features a very distinctive cap that seals and secures the bottle's contents with a metal lock, making it 100% leak-proof. The spout is ergonomic, with high flow that makes it easy to fill from the tap. By unscrewing the cap, it is very easy to wash and fill the bottle.