Great for our mums who have more than one pump or are catching their let down while feeding their baby - simply place cap on and put your full pump to the side while you continue feeding to stop contamination.Please note: These lids are designed to keep your milk safe and free of contamination and can fall off if left to move around in your bag or dropped so please make sure you empty your milk into our Haakaa milk storage glass set if you are needing to carry your milk around or store.To sterilise use one of the following methods: Steam sterilizing (electric or microwave) or boiling in water for 2-3 minutes.