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