Phonak - Unitron Hearing Aid Domes Comfortable. Silicone Domes for use with Thin Tube and Receiver-In-Canal Hearing Aids. Silicone Hearing Aid Domes fit the end of Thin-Tube and RIC Hearing Aids. Size? Measure the widest diameter of the silicone tip. Color: Smokey Hearing Aid Domes come four to a package (4)