I purchased these to use for my own personal perfume oils that I make. The first one I tried using was extremely tight when trying to get the roller ball fitting in. Once inside, the bottle though, it was great.
But, the 2nd time, I put a couple drops of liquid glycerin in with my oil. The roller ball fitting eased right in the bottle. A little glycerin also helps to bind your oil, therefore giving it a longer lasting scent.
I keep these bottles lying horizontally on my table or inside my purse and haven't had any issues with leakage. The size is perfect for my needs. I'm not sure how labels would stick to these but, I don't need them since I'm familiar with my own scents. One could always place a sticker on the black cap. I'd definitely recommend these for keeping your oils in.