Leak-proof closure for drinking bottles. The Sigg Active Spout closure is the perfect replacement for all Sigg narrow-mouth bottles or sports bottles with a WMB adapter. The innovative closure can be easily opened and closed with the mouth and is also reliably leak-proof, even when the bottle is upside down. Thus, the bottle cap is ideal for various sports activities. Additionally, the replacement part is particularly easy to clean thanks to its special design. The lid contains no harmful substances, including phthalates or estrogen-active substances.