to the various people wondering if their fit is an issue, here is a test method that has worked well for me.
put your customs in and leave them in for a few minutes so that the flexible part has a chance to warm up to your body temperature, then give them a good press into your ears, and then move your mouth or head around a bit, but not extremely, so that they kind of settle into the position that they will probably end up in over the long term.
then... go over to your sink and turn the water on, or better yet find a vacuum and turn it on. The point is you are going for a loud, consistent sound that will easily expose an imperfect seal. anything will do as long as its not a really low sub bass sound.. a blender is another good one.
now without music playing, listen to the sound of the sink or vacuum or whatever. then give the iem's another good press into your ears, them move your jaw or head again.. keep doing things like this and you'll very quickly notice if you have an incomplete seal on one or both ears because you will suddenly, or consistently hear the noise coming in. if you're really not sure.. start very very slowly pushing one of the iem's out of seal until you start hearing the noise get stronger, then press it back in and hold it where you know it is completely sealed.. then let go or move your jaw or whatever.. again it should become pretty obvious pretty quick if you have a shell that doesnt seal.
Now of course customs with no music playing will never completely block out the sound of something like a vacuum, but you should be able to tell very easily the difference between the "sealed out sound" and the sound leaking in through a broken seal.
hope this makes sense.
