I’ve bought these now twice, mostly because of the price. I almost solely pump so I go through a lot of bags. I wish the plastic was a little thicker because often the top parts flip in while I’m pouring in milk and I end up spilling. Though it doesn’t bother me enough to spend more on other brands.
I use spectrum breastmilk pump. I used to use lanshion breastmilk bag and my pump fits no problem, but this bag opening is slightly smaller than lanshion. But the bag is thick and great quality.
See detail on nuk-seal-breast-milk