A Custom UE Pro In Ear Monitor is made to fit. You must visit an audiologist in order to get a custom mold of the inside of your ear that will then be shipped to Ultimate Ears Pro. Click Find an Audiologist and follow the 3 easy steps to get your impressions. Audiologists should be familiar with the process of making an open mouth full shell impression with a CIC canal. If the audiologist isn’t familiar with these terms, Ultimate Ears Pro recommends finding one who is familiar with this process. Make sure you ask your audiologist how to best prepare for your appointment - some ask that you come prepared with clean ears and may advise a cleaning kit. Please check with them first. Please review and share the UE Audiologist Instructions with your audiologist.