Optical lead for digital audio interconnections. Available in 4mm diameter cable or better 5mm cable. The TOS type plug to Plug. TOS to TOS usually is used to connect Sky HD BluRay DVD Players to HiFi s (necessary sockets are required) plus some X-Boxes PC s and audio equipment have TOS sockets. Able to deliver digital 5.1 surround sound at the speed of light with very low loss in one cable.