Advantage for the covers:
light
easy to clean
easy installation
fits on all kinds of bottle caps of AVENT
Disadvantage
Suction can not be mounted parallel
For the subject sucker: Each bottle has a cap. The vacuum cleaner that fits perfectly between delivered screwed bottle with lid and cap. So we have always had the whole set here. Otherwise there is still div. Plastic storage facilities. Since you usually have a bag here should also make no circumstances this.
At home we use to touch the lid and the milk and to shake the bottle well. Since not a single drop goes out!
Purchase recommendation