Motion Pro is dedicated to producing the most versatile, unique and durable products for professional and home use. Motion Pro tools are designed to be simple to use, yet durable enough to withstand the harshest conditions. One of their goals is to offer tools of convenience. Do it right the first time with Motion Pro Tools. Fits 16 mm (5/8"), 18 mm (11/16"), or 21 mm (13/16") spark plugs. Ultra-strong tool steel construction. Slim skeleton profile. Use with a 3/8" square drive or 17 mm wrench. Innovative internal plug retention system. Protective black oxide coating. Easy to read laser-etched markings. Lightweight. Can be used as an axle holding tool on bikes with 17 mm or 19 mm internal hex axles; through hole allows use of screwdriver or holding rod. Patented design.