I found these are the best tip option for the Shure headphones I use (SCL-3) when using in-ear monitoring.
I'm a bass player and getting as good a seal in the ear canal as possible is crucial to the low end response from your IEMs. If you're not in the market for getting your own custom moulds made, these are the next best thing,
The singer in the band also uses these.
You do get a massive decibel reduction from what's going on in the outside world, so the isolation can take a little getting used to and we've taken to deploying a couple of ambient mics just for the IEM mix to combat this.