Great! but not for me
In my learning process I was inserting it at an upward angle like a tampon, but turns out you want to insert it completely horizonal (towards your tailbone). Once I did that I was able to get a nice seal.
It took me a few months to figure out how to get the cup to seal properly, and once I did it worked amazingly until about 2 hours, when it started to leak because it was full. Using the diva cup was a great way for me to learn more about the volume of my flow which I always thought was on the medium side but turns out it's heavy. I've switched to a disk and have been having a much better experience because its able to hold more!