On Amazon.com there's a choice between the Small, and a combo of Small + Medium. I'd rather go for a full pack of one size, but I'm not sure if the Medium Foam can be directly compared in size to the Medium Gel.
Personally I'm kind of between the fitting of the Gel small and medium; the small is almost perfect but a pinch too tiny, and the medium is a bit too large; it tends to fall out in one ear but fits snugly in the other.
I'm hoping that the foam version will compress better, so I can end up with the Medium, but I want to be sure before I pull the trigger on $30 worth of tips. I know there are some people on here who own both kinds of SuperTips, so I'm fishing for some first-hand experience answers.