5-Piece Spark Plug Socket Set for Most Vehicles 3/8-Inch Drive 6-Point Material: Fancy way of saying it's made of super strong steel (Chrome Vanadium) that's shiny and easy to wipe clean. Pieces: Comes with 5 different sockets that fit on a 3/8-inch drive ratchet or wrench. Socket Sizes: Includes 2 common size options (inches: 5/8", 3/4", 13/16") and 2 millimeter sizes (14mm, 18mm) to fit most spark plugs. Grip: Sockets have a rubber ring to hold the spark plug tight and a special 6-sided design that grips the flat sides of the plug, not the edges, to prevent damaging it. Markings: The sizes are clearly labeled on the sockets so you can easily find the right one you need.