This small in-ear earphone with the world's first 2-stage ear port and rustling-noise-reduction cord slider fits perfectly in your ears. The 2-stage ear port provides 6 different comfort zones for a variety of ear sizes in combination with the earpieces which come in 3 sizes. Approximately 70% of noise that comes from friction by cords and clothes is eliminated by the rustling-noise-reduction cord slider. The highly advanced ultra-thin exterior material allows the small earphone housing to go deep in your ears. Thanks to its comfort and airtight fit, the power bass booster exceeds its small appearance.