Those are regular IEMs. By custom parent comment means ones with a casing made specifically to fit inside your ear. Random example: http://vaiopocket.up.seesaa.

Those are regular IEMs. By custom parent comment means ones with a casing made specifically to fit inside your ear. Random example: http://vaiopocket.up.seesaa.net/image/sleek5.jpg http://vaiopocket.up.seesaa.net/image/sleek5.jpg, these can cost 3-4x more than a regular pair.