They're bigger than normal ones, but squish down. So before you put them in you need to squish them down so they fit in, after that they're fine. I usually have to use the smallest tips I can get so they fit in, these are snug but comfortable. When they're in the don't really move or rotate, I'm used to (having to) adjust the fit all the time, so it was a change to not have to touch them at all. Been for 3 hour long runs with them now, and haven't had to mess with them once.
If you usually have a M or L sized tip you may be able to get away with a smaller size so make sure you get a pack including all sizes. If you usually take the smallest size like me only bother ordering small ones IMO.
If the S500 will fit your headphones I'm quite happy to send you a pair.
That seems very promising.. I have range of headphone so the S500 would fit, let me know how much you want and I'll get it sorted, TY