Before using custom molded IEMs I used Etymotics with foam tips, which had much thicker foam than what I see on the Tinaudio product page. The isolation with foam is just as good, if properly inserted (same technique as with foam earplugs: roll to compress, insert deeply, and hold in place until fully expanded). But after only a few insertions the foam starts to lose its resiliency and sound-blocking effectiveness.

Custom IEMs can isolate noise almost as well as fully inserted foam earplugs, and they take only a second to insert or remove. The convenience and sound-blocking consistency are why I prefer them to "universal" tipped IEMs.