If you want to connect your headphones to a piano or receiver, this isn't always possible. Usually, a 6.3mm adapter isn't included with headphones, so you have to purchase them separately. To ensure that the adapter fits, you need to know what audio cable your headphones have. Can't disconnect the cable? You have a 3.5mm cable. Can the cable be disconnected and is the cable the same size on both sides? You're all good. On this page, you can find both adapters and cables with a 3.5mm to 6.3mm connector.