Sennheiser Airplane Airline In-Flight Adapter for Headphones with 1/8" 3.5mm double mono-plug Jack Use the Airline adapter to connect your own headphones to the in-flight entertainment system on the airplane for listening to music and movies The airline adapters converts a standard headphone stereo mini plug (1/8", 3.5mm) to a dual-prong airline jack Most of the headphones (portable, noise cancelling) are equipped with the 1/8" plug that will fit this adapter This adapter is designed with a smaller rounded "base" to fit with All 2-prong airline jack. (Some adapters doesn't and will not fit everywhere) Please note! Some newer airplane types accept the standard headphone plug direct, with no need for the adapter. There is a rarely used 3-prong jack that doesn't fit the adapter. Buying the airline adapter you are covered in the most cases