This product is made of a nice silicone material but has 2 significant design flaws that anyone using this for breastmilk storage would struggle with: (1) Though there are measurement markings on the outside, the container walls are completely opaque, so the markings are useless. You can't see how much milk is inside at all. (2) It's very difficult to clean. The only opening is the small pouring hole, which is too small and too awkward a reach to fit a cleaning brush. It looked as though the whole top could be removed for washing, but it can't.