Ive had both custom IEMs and custom earplugs. The sound isolation is generally better than nearly all foam tips, with some exceptions (ER6i, Er4p). The real di

Ive had both custom IEMs and custom earplugs. The sound isolation is generally better than nearly all foam tips, with some exceptions (ER6i, Er4p). The real difference is comfort. I can wear customs all day without experiencing any ear fatigue. Cable micro-phonics are also much quieter.