The Williams Sound NKL 005 is a 45" neckloop for use with hearing aids equipped with a T-coil switch or an induction earphone. The neckloop sends your audio directly to your T-Coil equipped hearing aid from your Williams Sound unit. To use plug in your 3.5mm adapter, place around the back of your neck, and it will couple the audio. It features a slide lock and break away device in the event the cord would get tangled.