The Yageo BK30-200-SI is a Polymer-Thermistor-Controlled (PTC) Resettable Fuse. It is a through-hole component, meaning that it is inserted into a PCB board rather than being surface-mounted. It has a RoHS-compliant design, meaning that it does not contain any hazardous materials or substances. The fuse is used to protect against over-current and over-temperature events, resetting automatically after the cause of the event has been removed. It has a maximum current of 200 Amps and a thermal protection of 155°C.