Instruct: Classify Amazon reviews into positive or negative sentiment
Query: They leak if frozen

I would say that about 25% of these bags leak. I have found that they leak less often if frozen flat,rather than upright, but they still leak. The best way to prevent leaking is to open the bag to release the vaccuum seal, then thaw it tilting down towards the top of the bag, since the bottom of the bag is where it breaks. This morning I forgot to do that, and I lost an ounce and a half to the sink. That's a lot of milk! I nearly cried. I've been working hard at keeping up my milk supply since I started taking my son to daycare, and it's a shame to keep losing milk due to leaks.I am debating getting the milk freeze trays from freshbaby that lets you freeze them into little 1-ounce milk cubes, then you can put them in a ziploc freezer bag after that.