The SP51P sound preference in-ear headphone allows you to tune the sound to fit your preference with the simple change of the tuning ports. Switch from pounding bass to a relaxing, neutral sound, to a fun sound with a little enhanced bass any time you want without spending for three different headphones. Change the sound based on your preference that time, with specific music genres, or even with different media players. Sound tuning is achieved by changing the rear tuning ports with settings for enhanced bass (metallic, installed), extreme bass (black), and balanced (silver). The in-ear design provides passive sound isolation and the 10 mm driver provides dynamic full range sound. Sound Preference Series allows the user to adjust the sound to suit their taste resulting in not just great sound, but great sound they way you prefer it. Features: Inline microphone supports hand-free talking for iPhone, and many mobile phones. Sound tuning rear ports allow the sound to be changed to your liking. Metallic color port is enhanced bass. Black color port is extreme bass. Silver color port is balanced sound. Powerful yet balanced full-range 10.0 mm dynamic driver delivers fantastic bass and accurate midrange and treble. In-ear design provides passive noise cancellation. Compatible with iPod, iPhone, iPad, Blackberry phones, and most Smartphones, MP3/CD/DVD players, computers, and other devices with a standard 3.5mm jack. Driver: 10.0 mm dynamic drivers. Housing: Metal housing with swappable rear tuning ports. Frequency Response: 15Hz - 20KHz. Sensitivity: 100 dB. Impedance: 16 ohms. Maximum Power Input: 40 mW. Connector: 4 pin 3.5mm gold plated 90 degree plug. Cable: Designer black 130 cm cable (51 in) with attached shirt clip. Microphone/Remote: Metal housed inline microphone and single button remote. 4 sets of eartips (small/medium/large silicon; bi-flange), clamshell zipper case.