Product details: Nalgene Sipper 53 mm Bottle Accessories Schwarz
Ideally to your Nalgene waterbottle 1 liter (32oz) with 5,3 cm opening (don't fit the Nalgene OTF). Simply insert into the neck of the bottle.
Solves the problem (the only disadvantage of the wide-necked bottles) that, when drinking, more comes from the bottle, than one can drink. Only infer for filling and cleaning.
• BPA free
• Ø 5,3 cm