Spark Plug Socket Set is a great tool for mechanics, homeowners or even do-it-yourselfers! Whether you're working on a car, motorcycle, or lawnmower, this spark plug set will get the job done. This features a premium grade rubber retaining ring that not only protects the ceramic insulator portion of your spark plug, but also securely holds the spark plug in place. So say goodbye to the days of dropping your spark plug in the engine bay or breaking your spark plug from dropping it. Along with the rubber retaining ring, the set also comes with adjustable sliding rails that features a ball bearing to conveniently secure and easily remove all your sockets. This convenient rail allows easy storage and keeps all your tools organized. And last but not least, buy with confidence knowing that the socket is constructed with Chrome Vanadium (Cr-V Steel) to ensure a long service life! SAE and METRIC sizes: 3/8 Drive SAE Sizes - 9/16 | 5/8 | 13/16 3/8 Inch, Metric Size 14 | 18 mm