Convenient jack output adpter attaches to the back of the WS4 headphone LCD earcup. Allows the use of an alternative headphone of your choice. Built in audio jack output (3.5mm, 1/8). Use the WS4 in your pocket or in a waterproof armband. See the target ID on the LCD. The WS4 can be used as a small but very efficient remote to adjust the most important settings.