Inner earphones that have achieved high sound quality and long life by adopting, for the first time in the world, extremely tough zirconia ceramics for their ear-buds. Enables a clear stereo almost original sound by suppressing resonance. They look brand new for years because they are surprisingly resistant to scratches and do not corrode under harsh conditions. Removable cords have been adopted that can be replaced when broken, showing that these are definitely not disposable earphones. The cords can be replaced by “Hi-fi cords” or short “60 cm cords,” allowing easy customization.