An adapter converting a 3.5mm jack to a 6.3mm jack is often used to convert some professional headphones and other audio devices. These devices include but are not limited to headphone amplifiers, some instruments, audio interfaces, digital-to-analog converters, mixing consoles and more. For example, These 3.5mm to 6.3mm adaptors are perfect for use with Coomber boxes, as it means you do not need to purchase seperate headphones. This means, you can use your Coomber box with your modern, durable headphones with ease at a low cost.