The 751KD05J is a varistor manufactured by Yageo. It is a through-hole RoHS compliant component and is rated to be 5mm in diameter. The varistor has a voltage rating of 750V, an AC current rating of 1A, and a DC current rating of 0.5A. It also has impedance between 4-7 Ohms and a tolerance between 0-30%. It is designed to protect sensitive components and circuits from transients and is commonly used in power supplies, audio circuits, and switchboards.