Pumping and storing breastmilk can be a tricky and time consuming process. After trying the bags with the little clippy things with my first child I knew I had to find something easier when my next bundle of joy arrived. I received the Avent Via Breast Milk Storage Kit at my baby shower and have never looked back to those leaky bags. The cups attach easily to my Avent breast pump so I can pump the milk right into the container which is much more sanitary than some of the others on the marker. When done the lid twists on to prevent spills. I have practiced several times by turning the product upside down and shaking it and no milk comes pouring out! This is so very important to me as I have a hard time pumping a lot of milk. I do not want wasted milk spilling out in the freezer. These containers also allow for easy stacking in the freezer and do not end up getting crushed like the bag method. The cups are easy to wash and reuse several times which makes them environmentally-friendly too. The storage containers also can be written easily with a sharpy so that you can mark the day the milk was expressed. The only down side to the storage kit is that you need to make sure the tops are on properly as it is easy to miss a thread and end up with milk spilled everywhere. The storage kit can be a little costly, especially if you like to stock up your milk. I have found them worth the money and still a whole lot cheaper than formula.