NGK Insulators, Ltd. is a Japanese ceramics company. It primarily produces insulators but also produces other products, especially ceramic products. NGK is headquartered in Tokyo and is listed on the Nikkei 225, which is an index of the Tokyo Stock Exchange. It is also listed in the Osaka Securities Exchange, the Nagoya Stock Exchange, and the Sapporo Securities Exchange all under listing code 5333. NGK stands for Nippon Gaishi Kaisha. Wikipedia