This mode conditioning fiber optic cable is made with Corning glass fiber and consists of a duplex LC male on one end and 2 simplex ST male on the other end. It allows you to connect singlemode equipment such as, gigabit routers and switches, to existing multimode cable environments. It does so by emulating a LED light source from a laser light source by off-setting the fusion splice of the singlemode leg onto the multimode cable. They are typically purchased in pairs (one for each end of the cable run) and used in multimode cable runs over 300m. The singlemode cable leg is connected to transmit on the equipment end.