There are no noticeable scratches or stains, and it is in good condition. This is an offering of the main unit only. The **"Billie Jean"** by Astell&Kern and JH Audio, a collaboration, is a model that serves as the entry-middle class of "THE SIREN Series" designed by Jerry Harvey, a pioneer in IEMs for professional musicians. Type: Universal Fit IEM Driver: Custom-made BA driver (2-way 2BA) Impedance: 18Ω Noise Isolation: -26dB Connector: Custom IEM 2pin (0.78mm) Color: Purple Released in 2018, it is inspired by Michael Jackson's famous song of the same name. The main features and attractions are organized and explained below. 1. Main Features and Technology The biggest feature of this model is that JH Audio's high-end technology is condensed into a more compact and accessible package. 2-way Dual BA Driver Configuration It is equipped with a total of two custom BA (Balanced Armature) drivers: one for high frequencies and one for mid-low frequencies. While simple, it aims for flat and wide-range playback with low distortion across all frequency ranges. Proprietary "freqphase" Technology This is a patented technology of JH Audio that accurately controls the time axis and phase between multiple drivers. This minimizes the lag when sound reaches the ear, achieving accurate sound image localization and clear sound. Acoustic Chamber Sound Bore A new design that incorporates a cavity (chamber) at the tip of the nozzle. It optimizes the characteristics of high frequencies in particular and also prevents foreign matter from entering the conduit. 2. Sound Characteristics It is based on the **"Rock 'n' Roll Sound"** typical of JH Audio. Powerful Low Frequencies and Clear Mid-High Frequencies: It features thick low frequencies that you wouldn't expect from two BA drivers and clear mid-range vocals. Genre Suitability: It is especially compatible with pop, rock, and EDM, and is suitable for a dynamic music experience with a sharp sound. Monitor Performance: It boasts reference quality that can be used in professional settings, and the resolution is also at a very high level for its price range (around 40,000 yen at the time of release).