Armstrong 11-501 3/8-Inch Drive Spark Plug Socket with 5/8-Inch Rubber Insert Made in the USA - quality and availability EYE-D markings optimize size visibility Manufactured from high alloy steel using the most up-to-date manufacturing process and heat treat for greater strength and durability Precision cold formed of special steel for exact, consistent dimensions and greater strength Proudly made in the USA with a lifetime warranty