The OTF 350ml with cunning stopper technology. One handed pressure stopper for quick and comfortable drinking during your outdoor activity. The lid can be made 100% leak proof by means of a metal stirrup. Unscrewing the complete lid makes for easy cleaning and refilling. Made of Copolyester with a Polypropylene lid. Suitable for dish washers. Easy handling and fits in current bottle holders - bikes too. As normal with Nalgene there is a liquid level e.g. for the safe mixing of mineral drinks. A perfect solution in excellent quality.