I opened my Obagi Medical Professional C Serum 10% yesterday and put the dropper into the bottle. I tightened the cap so it would not leak, but when I went to use it this morning, I noticed it had been leaking in my drawer. I lost about 1/3 of my product. When I looked closer, I noticed that the rubber part of the dropper was not sealed completely and had been leaking. I was so disappointed. I reached out to Customer service and talked to them about the issue and they are sending a replacement bottle. I wasn't sure what to expect when I reached out, but they were so easy to work with. Definitely purchase from the again!