I absolutely LOVE these!! They are the perfect size for so many things. They are totally leak proof. I have no fear dropping it in my purse with something liquid in it. I used 3 different ones and didn't understand the comments about the lids being so hard to get on and off. But then the 4th one I did have an issue. But it's easily resolved. I ran it under hot water like someone mentioned to make it more pliable. And then put the lid on with a bit of difficulty. Then left it for 10 min. Came back and removed the lid with ease and put it back on very easily. So I would say when you get them and wash them, be sure to use hot water from the tap and then put lids on then. Leave them and come back and open them and they should be set. But like I said, I only experienced that with one so far. Don't let that keep you from ordering. These are FANTASTIC!!!!