The Vintage Spark Plug Feeler Gauge KASTAR # 21A is a rare and sought-after thickness gauge used in the automotive industry. Made in the United States by the trusted brand KASTAR, this tool is perfect for measuring the thickness of spark plug wires and other components in vehicles. With a focus on precision and durability, this gauge is a valuable addition to any mechanic’s toolbox, offering a unique and essential function for automotive maintenance and repair.