Official Apple USB-C to 3.5mm Jack Adapter
Official Apple USB-C to 3.5mm Headphone Jack Adapter.
If you want to use your own headphones, but have an iPhone or iPad with NO 3.5mm jack (most of them these days) this is the perfect accessory for you.
With a USB-C connection on one end, and a female 3.5mm Jack connector on the other, just simply plug it in to you iPhone or iPad, and then connect your headphones.
Connectivity: USB-C to 3.5mm Jack Adaptor